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.Net frameword Resources ( vb.net , asp.net etc...)

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· When was .NET announced?
Bill Gates delivered a keynote at Forum 2000, held June 22, 2000,
outlining the .NET 'vision'. The July 2000 PDC had a number of sessions
on .NET technology, and delegates were given CDs containing a
pre-release version of the .NET framework/SDK and Visual Studio.NET.

· When was the first version of .NET released?
The final version of the 1.0 SDK and runtime was made publicly
available around 6pm PST on 15-Jan-2002. At the same time, the final
version of Visual Studio.NET was made available to MSDN subscribers.

· What platforms does the .NET Framework run on?
The runtime supports Windows XP, Windows 2000, NT4 SP6a and Windows
ME/98. Windows 95 is not supported. Some parts of the framework do not
work on all platforms - for example, ASP.NET is only supported on
Windows XP and Windows 2000. Windows 98/ME cannot be used for
development.
IIS is not supported on Windows XP Home Edition, and so cannot be used
to host ASP.NET. However, the ASP.NET Web Matrix web server does run on
XP Home.
The Mono project is attempting to implement the .NET framework on
Linux.

· What is the CLR?
CLR = Common Language Runtime. The CLR is a set of standard resources
that (in theory) any .NET program can take advantage of, regardless of
programming language. Robert Schmidt (Microsoft) lists the following
CLR resources in his MSDN PDC# article:
Object-oriented programming model (inheritance, polymorphism, exception
handling, garbage collection)
Security model
Type system
All .NET base classes
Many .NET framework classes
Development, debugging, and profiling tools
Execution and code management
IL-to-native translators and optimizers
What this means is that in the .NET world, different programming
languages will be more equal in capability than they have ever been
before, although clearly not all languages will support all CLR
services.

· What is the CTS?
CTS = Common Type System. This is the range of types that the .NET
runtime understands, and therefore that .NET applications can use.
However note that not all .NET languages will support all the types in
the CTS. The CTS is a superset of the CLS.

· What is the CLS?
CLS = Common Language Specification. This is a subset of the CTS which
all .NET languages are expected to support. The idea is that any
program, which uses CLS-compliant types, can interoperate with any .NET
program written in any language.
In theory this allows very tight interop between different .NET
languages - for example allowing a C# class to inherit from a VB class.

· What is IL?
IL = Intermediate Language. Also known as MSIL (Microsoft Intermediate
Language) or CIL (Common Intermediate Language). All .NET source code
(of any language) is compiled to IL. The IL is then converted to
machine code at the point where the software is installed, or at
run-time by a Just-In-Time (JIT) compiler.

· What does 'managed' mean in the .NET context?
The term 'managed' is the cause of much confusion. It is used in
various places within .NET, meaning slightly different things.Managed
code: The .NET framework provides several core run-time services to the
programs that run within it - for example
exception handling and security. For these services to work, the code
must provide a minimum level of information to the runtime.
Such code is called managed code. All C# and Visual Basic.NET code is
managed by default. VS7 C++ code is not managed by default, but the
compiler can produce managed code by specifying a command-line switch
(/com+).

Managed data: This is data that is allocated and de-allocated by the
..NET runtime's garbage collector. C# and VB.NET data is always managed.
VS7 C++ data is unmanaged by default, even when using the /com+ switch,
but it can be marked as managed using the __gc keyword.Managed classes:
This is usually referred to in the context of Managed Extensions (ME)
for C++. When using ME C++, a class can be marked with the __gc
keyword. As the name suggests, this means that the memory for instances
of the class is managed by the garbage collector, but it also means
more than that. The class becomes a fully paid-up member of the .NET
community with the benefits and restrictions that brings. An example of
a benefit is proper interop with classes written in other languages -
for example, a managed C++ class can inherit from a VB class. An
example of a restriction is that a managed class can only inherit from
one base class.

· What is reflection?
All .NET compilers produce metadata about the types defined in the
modules they produce. This metadata is packaged along with the module
(modules in turn are packaged together in assemblies), and can be
accessed by a mechanism called reflection. The System.Reflection
namespace contains classes that can be used to interrogate the types
for a module/assembly.

Using reflection to access .NET metadata is very similar to using
ITypeLib/ITypeInfo to access type library data in COM, and it is used
for similar purposes - e.g. determining data type sizes for marshaling
data across context/process/machine boundaries.
Reflection can also be used to dynamically invoke methods (see
System.Type.InvokeMember ) , or even create types dynamically at
run-time (see System.Reflection.Emit.TypeBuilder).

· What is the difference between Finalize and Dispose (Garbage
collection) ?
Class instances often encapsulate control over resources that are not
managed by the runtime, such as window handles (HWND), database
connections, and so on. Therefore, you should provide both an explicit
and an implicit way to free those resources. Provide implicit control
by implementing the protected Finalize Method on an object (destructor
syntax in C# and the Managed Extensions for C++). The garbage collector
calls this method at some point after there are no longer any valid
references to the object. In some cases, you might want to provide
programmers using an object with the ability to explicitly release
these external resources before the garbage collector frees the object.
If an external resource is scarce or expensive, better performance can
be achieved if the programmer explicitly releases resources when they
are no longer being used. To provide explicit control, implement the
Dispose method provided by the IDisposable Interface. The consumer of
the object should call this method when it is done using the object.
Dispose can be called even if other references to the object are alive.
Note that even when you provide explicit control by way of Dispose, you
should provide implicit cleanup using the Finalize method. Finalize
provides a backup to prevent resources from permanently leaking if the
programmer fails to call Dispose.

· What is Partial Assembly References?
Full Assembly reference: A full assembly reference includes the
assembly's text name, version, culture, and public key token (if the
assembly has a strong name). A full assembly reference is required if
you reference any assembly that is part of the common
language runtime or any assembly located in the global assembly cache.

Partial Assembly reference: We can dynamically reference an assembly by
providing only partial information, such as specifying only the
assembly name. When you specify a partial assembly reference, the
runtime looks for the assembly only in the application
directory.

We can make partial references to an assembly in your code one of the
following ways:

-Use a method such as System.Reflection.Assembly.Load and specify
only a partial reference. The runtime checks for the assembly in the
application directory.

-Use the System.Reflection.Assembly.LoadWithPartialName method and
specify only a partial reference. The runtime checks for the assembly
in the application directory and in the global assembly cache

· Changes to which portion of version number indicates an
incompatible change?
Major or minor. Changes to the major or minor portion of the version
number indicate an incompatible change. Under this convention then,
version 2.0.0.0 would be considered incompatible with version 1.0.0.0.
Examples of an incompatible change would be a change to the types of
some method parameters or the removal of a type or method altogether.
Build. The Build number is typically used to distinguish between daily
builds or smaller compatible releases. Revision. Changes to the
revision number are typically reserved for an incremental build needed
to fix a particular bug. You'll sometimes hear this referred to as the
"emergency bug fix" number in that the revision is what is often
changed when a fix to a specific bug is shipped to a customer.

· What is side-by-side execution? Can two application one using
private assembly and other using Shared assembly be stated as a
side-by-side executables?
Side-by-side execution is the ability to run multiple versions of an
application or component on the same computer. You can have multiple
versions of the common language runtime, and multiple versions of
applications and components that use a version of the runtime, on the
same computer at the same time. Since versioning is only applied to
shared assemblies, and not to private assemblies, two application one
using private assembly and one using shared assembly cannot be stated
as side-by-side
executables.

· Why string are called Immutable data Type ?
The memory representation of string is an Array of Characters, So on
re-assigning the new array of Char is formed & the start address is
changed . Thus keeping the Old string in Memory for Garbage Collector
to be disposed.

· What does assert() method do?
In debug compilation, assert takes in a Boolean condition as a
parameter, and shows the error dialog if the condition is false. The
program proceeds without any interruption if the condition is true.

· What's the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use
Trace class for both debug and release builds.

· Why are there five tracing levels in
System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose. For applications that are
constantly running you run the risk of overloading the machine and the
hard drive. Five levels range from None to Verbose, allowing you to
fine-tune the tracing activities.

· Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the
constructor.

· How do assemblies find each other?
By searching directory paths. There are several factors which can
affect the path (such as the AppDomain host, and application
configuration files), but for private assemblies the search path is
normally the application's directory and its sub-directories. For
shared assemblies, the search path is normally same as the private
assembly path plus the shared assembly cache.

· How does assembly versioning work?
Each assembly has a version number called the compatibility version.
Also each reference to an assembly (from another assembly) includes
both the name and version of the referenced assembly.The version number
has four numeric parts (e.g. 5.5.2.33). Assemblies with either of the
first two parts different are normally viewed as incompatible. If the
first two parts are the same, but the third is different, the
assemblies are deemed as 'maybe compatible'. If only the fourth part is
different, the assemblies are deemed compatible. However, this is just
the default guideline - it is the version policy that decides to what
extent these rules are enforced. The version policy can be specified
via the application configuration file.

· What is garbage collection?
Garbage collection is a system whereby a run-time component takes
responsibility for managing the lifetime of objects and the heap memory
that they occupy. This concept is not new to .NET - Java and many other
languages/runtimes have used garbage collection for some time.

· Why doesn't the .NET runtime offer deterministic destruction?
Because of the garbage collection algorithm. The .NET garbage collector
works by periodically running through a list of all the objects that
are currently being referenced by an application. All the objects that
it doesn't find during this search are ready to be destroyed and the
memory reclaimed. The implication of this algorithm is that the runtime
doesn't get notified immediately when the final reference on an object
goes away - it only finds out during the next sweep of the heap.
Futhermore, this type of algorithm works best by performing the garbage
collection sweep as rarely as possible. Normally heap exhaustion is the
trigger for a collection sweep.

· Is the lack of deterministic destruction in .NET a problem?
It's certainly an issue that affects component design. If you have
objects that maintain expensive or scarce resources (e.g. database
locks), you need to provide some way for the client to tell the object
to release the resource when it is done. Microsoft recommend that you
provide a method called Dispose() for this purpose. However, this
causes problems for distributed objects - in a distributed system who
calls the Dispose() method? Some form of reference-counting or
ownership-management mechanism is needed to handle distributed objects
- unfortunately the runtime offers no help with this.

· What is serialization?
Serialization is the process of converting an object into a stream of
bytes. Deserialization is the opposite process of creating an object
from a stream of bytes. Serialization / Deserialization is mostly used
to transport objects (e.g. during remoting), or to persist
objects (e.g. to a file or database).

· Does the .NET Framework have in-built support for serialization?
There are two separate mechanisms provided by the .NET class library -
XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses
XmlSerializer for Web Services, and uses SoapFormatter/BinaryFormatter
for remoting. Both are available for use in your own code.

· Can I customise the serialization process?
Yes. XmlSerializer supports a range of attributes that can be used to
configure serialization for a particular class. For example, a field or
property can be marked with the [XmlIgnore] attribute to exclude it
from serialization. Another example is the [XmlElement]
attribute, which can be used to specify the XML element name to be used
for a particular property or field.
Serialization via SoapFormatter/BinaryFormatter can also be controlled
to some extent by attributes. For example, the [NonSerialized]
attribute is the equivalent of XmlSerializer's [XmlIgnore] attribute.
Ultimate control of the serialization process can be acheived by
implementing the the ISerializable interface on the class whose
instances are to be serialized.

· Why is XmlSerializer so slow?
There is a once-per-process-per-type overhead with XmlSerializer. So
the first time you serialize or deserialize an object of a given type
in an application, there is a significant delay. This normally doesn't
matter, but it may mean, for example, that XmlSerializer is a poor
choice for loading configuration settings during startup of a GUI
application.

· Why do I get errors when I try to serialize a Hashtable?
XmlSerializer will refuse to serialize instances of any class that
implements IDictionary, e.g. Hashtable. SoapFormatter and
BinaryFormatter do not have this restriction.

· What are attributes?
There are at least two types of .NET attribute. The first type I will
refer to as a metadata attribute - it allows some data to be attached
to a class or method. This data becomes part of the metadata for the
class, and (like other class metadata) can be accessed via reflection.
The other type of attribute is a context attribute. Context attributes
use a similar syntax to metadata attributes but they are fundamentally
different. Context attributes provide an interception mechanism whereby
instance activation and method calls can be
pre- and/or post-processed.

· How does CAS work?
The CAS security policy revolves around two key concepts - code groups
and permissions. Each .NET assembly is a member of a particular code
group, and each code group is granted the permissions specified in a
named permission set.
For example, using the default security policy, a control downloaded
from a web site belongs to the 'Zone - Internet' code group, which
adheres to the permissions defined by the 'Internet' named permission
set. (Naturally the 'Internet' named permission set represents a very
restrictive range of permissions.)

· Who defines the CAS code groups?
Microsoft defines some default ones, but you can modify these and even
create your own. To see the code groups defined on your system, run
'caspol -lg' from the command-line. On my system it looks like this:
Level = Machine
Code Groups:
1. All code: Nothing
1.1. Zone - MyComputer: FullTrust
1.1.1. Honor SkipVerification requests: SkipVerification
1.2. Zone - Intranet: LocalIntranet
1.3. Zone - Internet: Internet
1.4. Zone - Untrusted: Nothing
1.5. Zone - Trusted: Internet
1.6. StrongName -
00240000048000009400000006020000002400005253413100 04000003
000000CFCB3291AA715FE99D40D49040336F9056D7886FED46 775BC7BB5430BA4444FEF8348EBD06
F962F39776AE4DC3B7B04A7FE6F49F25F740423EBF2C0B8969 8D8D08AC48D69CED0FC8F83B465E08
07AC11EC1DCC7D054E807A43336DDE408A5393A48556123272 CEEEE72F1660B71927D38561AABF5C
AC1DF1734633C602F8F2D5:
Note the hierarchy of code groups - the top of the hierarchy is the
most general ('All code'), which is then sub-divided into several
groups, each of which in turn can be sub-divided. Also note that
(somewhat counter-intuitively) a sub-group can be associated with a
more permissive permission set than its parent.

· How do I define my own code group?
Use caspol. For example, suppose you trust code from www.mydomain.com
and you want it have full access to your system, but you want to keep
the default restrictions for all other internet sites. To achieve this,
you would add a new code group as a sub-group of the 'Zone - Internet'
group, like this:
caspol -ag 1.3 -site www.mydomain.com FullTrust
Now if you run caspol -lg you will see that the new group has been
added as group 1.3.1:

1.3. Zone - Internet: Internet
1.3.1. Site - www.mydomain.com: FullTrust

Note that the numeric label (1.3.1) is just a caspol invention to make
the code groups easy to manipulate from the command-line. The
underlying runtime never sees it.

· How do I change the permission set for a code group?
Use caspol. If you are the machine administrator, you can operate at
the 'machine' level - which means not only that the changes you make
become the default for the machine, but also that users cannot change
the permissions to be more permissive. If you are a normal (non-admin)
user you can still modify the permissions, but only to make them more
restrictive. For example, to allow intranet code to do what it likes
you might do this:
caspol -cg 1.2 FullTrust
Note that because this is more permissive than the default policy (on a
standard system), you should only do this at the machine level - doing
it at the user level will have no effect.

· I can't be bothered with all this CAS stuff. Can I turn it off?
Yes, as long as you are an administrator. Just run: caspol -s off

· Can I look at the IL for an assembly?
Yes. MS supply a tool called Ildasm which can be used to view the
metadata and IL for an assembly.

· Can source code be reverse-engineered from IL?
Yes, it is often relatively straightforward to regenerate high-level
source (e.g. C#) from IL.

· How can I stop my code being reverse-engineered from IL?
There is currently no simple way to stop code being reverse-engineered
from IL. In future it is likely that IL obfuscation tools will become
available, either from MS or from third parties. These tools work by
'optimising' the IL in such a way that reverse-engineering becomes much
more difficult.
Of course if you are writing web services then reverse-engineering is
not a problem as clients do not have access to your IL.

· Is there built-in support for tracing/logging?
Yes, in the System.Diagnostics namespace. There are two main classes
that deal with tracing - Debug and Trace. They both work in a similar
way - the difference is that tracing from the Debug class only works in
builds that have the DEBUG symbol defined, whereas tracing from the
Trace class only works in builds that have the TRACE symbol defined.
Typically this means that you should use
System.Diagnostics.Trace.WriteLine for tracing that you want to work in
debug and release builds, and System.Diagnostics.Debug.WriteLine for
tracing that you want to work only in debug builds.

· Can I redirect tracing to a file?
Yes. The Debug and Trace classes both have a Listeners property, which
is a collection of sinks that receive the tracing that you send via
Debug.WriteLine and Trace.WriteLine respectively. By default the
Listeners collection contains a single sink, which is an
instance of the DefaultTraceListener class. This sends output to the
Win32 OutputDebugString() function and also the
System.Diagnostics.Debugger.Log() method. This is useful when
debugging, but if you're trying to trace a problem at a customer site,
redirecting the output to a file is more appropriate. Fortunately, the
TextWriterTraceListener class is provided for this purpose.

· What are the contents of assembly?
In general, a static assembly can consist of four elements:
The assembly manifest, which contains assembly metadata.
Type metadata.
Microsoft intermediate language (MSIL) code that implements the types.

A set of resources.

· What is GC (Garbage Collection) and how it works
One of the good features of the CLR is Garbage Collection, which runs
in the background collecting unused object references, freeing us from
having to ensure we always destroy them. In reality the time difference
between you releasing the object instance and it being garbage
collected is likely to be very small, since the GC is always running.
[The process of transitively tracing through all pointers to actively
used objects in order to locate all objects that can be referenced, and
then arranging to reuse any heap memory that was not found during this
trace. The common language runtime garbage collector also compacts the
memory that is in use to reduce the working space needed for the heap.]

Heap:
A portion of memory reserved for a program to use for the temporary
storage of data structures whose existence or size cannot be determined
until the program is running.

· Differnce between Managed code and unmanaged code ?
Managed Code:
Code that runs under a "contract of cooperation" with the common
language runtime. Managed code must supply the metadata necessary for
the runtime to provide services such as memory management,
cross-language integration, code access security, and
automatic lifetime control of objects. All code based on Microsoft
intermediate language (MSIL) executes as managed code.

Un-Managed Code:
Code that is created without regard for the conventions and
requirements of the common language runtime. Unmanaged code executes in
the common language runtime environment with minimal services (for
example, no garbage collection, limited debugging, and so on).

· What is MSIL, IL, CTS and, CLR ?

MSIL: (Microsoft intermediate language)
When compiling to managed code, the compiler translates your source
code into Microsoft intermediate language (MSIL), which is a
CPU-independent set of instructions that can be efficiently converted
to native code. MSIL includes instructions for loading, storing,
initializing, and calling methods on objects, as well as instructions
for arithmetic and logical operations, control flow, direct memory
access, exception handling, and other operations. Before code can be
executed, MSIL must be converted to CPU-specific code, usually by a
just-in-time (JIT) compiler. Because the common language runtime
supplies one or more JIT compilers for each computer architecture it
supports, the same set of MSIL can be JIT-compiled and executed on any
supported architecture.
When a compiler produces MSIL, it also produces metadata. Metadata
describes the types in your code, including the definition of each
type, the signatures of each type's members, the members that your code
references, and other data that the runtime uses at execution time. The
MSIL and metadata are contained in a portable executable (PE) file that
is based on and extends the published Microsoft PE and Common Object
File Format (COFF) used historically for executable content. This file
format, which accommodates MSIL or native code as well as metadata,
enables the operating system to recognize common language runtime
images. The presence of metadata in the file along with the MSIL
enables your code to describe itself, which means that there is no need
for type libraries or Interface Definition Language (IDL). The runtime
locates and extracts the metadata from the file as needed during
execution.

IL: (Intermediate Language)
A language used as the output of a number of compilers and as the input
to a just-in-time (JIT) compiler. The common language runtime includes
a JIT compiler for converting MSIL to native code.

CTS: (Common Type System)
The specification that determines how the common language runtime
defines, uses, and manages types

CLR: (Common Language Runtime)
The engine at the core of managed code execution. The runtime supplies
managed code with services such as cross-language integration, code
access security, object lifetime management, and debugging and
profiling support.

· What is Reference type and value type ?
Reference Type:
Reference types are allocated on the managed CLR heap, just like object
types.
A data type that is stored as a reference to the value's location. The
value of a reference type is the location of the sequence of bits that
represent the type's data. Reference types can be self-describing
types, pointer types, or interface types

Value Type:
Value types are allocated on the stack just like primitive types in
VBScript, VB6 and C/C++. Value types are not instantiated using new go
out of scope when the function they are defined within returns.
Value types in the CLR are defined as types that derive from
system.valueType.

A data type that fully describes a value by specifying the sequence of
bits that constitutes the value's representation. Type information for
a value type instance is not stored with the instance at run time, but
it is available in metadata. Value type instances can be treated as
objects using boxing.

· What is Boxing and unboxing ?
Boxing:
The conversion of a value type instance to an object, which implies
that the instance will carry full type information at run time and will
be allocated in the heap. The Microsoft intermediate language (MSIL)
instruction set's box instruction converts a value type to an object by
making a copy of the value type and embedding it in a newly allocated
object.

Un-Boxing:
The conversion of an object instance to a value type.

· What is JIT and how is works ?
An acronym for "just-in-time," a phrase that describes an action that
is taken only when it becomes necessary, such as just-in-time
compilation or just-in-time object activation

· What is portable executable (PE) ?
The file format used for executable programs and for files to be linked
together to form executable programs

· What is strong name?
A name that consists of an assembly's identity-its simple text name,
version number, and culture information (if provided)-strengthened by
a public key and a digital signature generated over the assembly.
Because the assembly manifest contains file hashes for all the files
that constitute the assembly implementation, it is sufficient to
generate the digital signature over just the one file in the assembly
that contains the assembly manifest. Assemblies with the same strong
name are expected to be identical

· What is global assembly cache?
A machine-wide code cache that stores assemblies specifically installed
to be shared by many applications on the computer. Applications
deployed in the global assembly cache must have a strong name.

· What is difference between constants, readonly and, static ?
Constants: The value can't be changed
Read-only: The value will be initialized only once from the constructor
of the class.
Static: Value can be initialized once.

· What is difference between shared and public?
An assembly that can be referenced by more than one application. An
assembly must be explicitly built to be shared by giving it a
cryptographically strong name.

· What is namespace used for loading assemblies at run time and name
the methods?
System.Reflection

· What are the types of authentication in .net?
We have three types of authentication:
1. Form authentication
2. Windows authentication
3. Passport
This has to be declared in web.config file.

· What is the difference between a Struct and a Class ?
The struct type is suitable for representing lightweight objects such
as Point, Rectangle, and Color. Although it is possible to represent a
point as a class, a struct is more efficient in some scenarios. For
example, if you declare an array of 1000 Point objects,
you will allocate additional memory for referencing each object. In
this case, the struct is less expensive.
When you create a struct object using the new operator, it gets created
and the appropriate constructor is called. Unlike classes, structs can
be instantiated without using the new operator. If you do not use new,
the fields will remain unassigned and the object cannot be used until
all of the fields are initialized. It is an error to declare a default
(parameterless) constructor for a struct. A default constructor is
always provided to initialize the struct members to their default
values.
It is an error to initialize an instance field in a struct.
There is no inheritance for structs as there is for classes. A struct
cannot inherit from another struct or class, and it cannot be the base
of a class. Structs, however, inherit from the base class Object. A
struct can implement interfaces, and it does that exactly as classes
do.
A struct is a value type, while a class is a reference type.

· How big is the datatype int in .NET?
32 bits.

· How big is the char?
16 bits (Unicode).

· How do you initiate a string without escaping each backslash?
Put an @ sign in front of the double-quoted string.

· What's the access level of the visibility type internal?
Current application.

· Explain encapsulation?
The implementation is hidden, the interface is exposed.

· What data type should you use if you want an 8-bit value that's
signed?
sbyte.

· Speaking of Boolean data types, what's different between C# and
C/C++?
There's no conversion between 0 and false, as well as any other number
and true, like in C/C++.

· Where are the value-type variables allocated in the computer RAM?
Stack.

· Where do the reference-type variables go in the RAM?
The references go on the stack, while the objects themselves go on the
heap.

· What is the difference between the value-type variables and
reference-type variables in terms of garbage collection?
The value-type variables are not garbage-collected, they just fall off
the stack when they fall out of scope, GC picks up the reference-type
objects when their references go null.

· How do you convert a string into an integer in .NET?
Int32.Parse(string)

· How do you box a primitive data type variable?
Assign it to the object, pass an object.

· Why do you need to box a primitive variable?
Pass it by reference.

· What's the difference between Java and .NET garbage collectors?
Sun left the implementation of a specific garbage collector up to the
JRE developer, so their performance varies widely, depending on whose
JRE you're using. Microsoft standardized on their garbage collection.

· How do you enforce garbage collection in .NET?
System.GC.Collect();

· What's different about namespace declaration when comparing that to
package declaration in Java?
No semicolon.

· What's the difference between const and readonly?
You can initialize readonly variables to some runtime values. Let's say
your program uses current date and time as one of the values that won't
change. This way you declare public readonly string DateT = new
DateTime().ToString().

· What happens when you encounter a continue statement inside the for
loop?
The code for the rest of the loop is ignored, the control is
transferred back to the beginning of the loop.

· What's the advantage of using System.Text.StringBuilder over
System.String?
StringBuilder is more efficient in the cases, where a lot of
manipulation is done to the text. Strings are immutable, so each time
it's being operated on, a new instance is created.

· Can you store multiple data types in System.Array?
No.

· What's the difference between the System.Array.CopyTo() and
System.Array.Clone()?
The first one performs a deep copy of the array, the second one
performs a shallow copy.

· How can you sort the elements of the array in descending order?
By calling Sort() and then Reverse() methods.

· What's the .NET datatype that allows the retrieval of data by a
unique key?
HashTable.

· What's class SortedList underneath?
A sorted Hash Table.

· Will finally block get executed if the exception had not occurred?
Yes.

· Can multiple catch blocks be executed?
No, once the proper catch code fires off, the control is transferred to
the finally block (if there are any), and then whatever follows the
finally block.

· Why is it a bad idea to throw your own exceptions?
Well, if at that point you know that an error has occurred, then why
not write the proper code to handle that error instead of passing a new
Exception object to the catch block? Throwing your own exceptions
signifies some design flaws in the project.

· What's a delegate?
A delegate object encapsulates a reference to a method. In C++ they
were referred to as function pointers.

· What's a multicast delegate?
It's a delegate that points to and eventually fires off several
methods.

· How's the DLL Hell problem solved in .NET?
Assembly versioning allows the application to specify not only the
library it needs to run (which was available under Win32), but also
the version of the assembly.

· What are the ways to deploy an assembly?
An MSI installer, a CAB archive, and XCOPY command.

· What's a satellite assembly?
When you write a multilingual or multi-cultural application in .NET,
and want to distribute the core application separately from the
localized modules, the localized assemblies that modify the core
application are called satellite assemblies.

· What namespaces are necessary to create a localized application?
System.Globalization, System.Resources.

· What does assert() do?
In debug compilation, assert takes in a Boolean condition as a
parameter, and shows the error dialog if the condition is false. The
program proceeds without any interruption if the condition is true.

· What's the difference between the Debug class and Trace class?
Documentation looks the same. Use Debug class for debug builds, use
Trace class for both debug and release builds.

· Why are there five tracing levels in
System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that
are constantly running you run the risk of overloading the machine and
the hard drive there. Five levels range from None to Verbose, allowing
to fine-tune the tracing activities.

· Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the
constructor.

· What namespaces are necessary to create a localized application?
System.Globalization, System.Resources.

· What are three test cases you should go through in unit testing?
Positive test cases (correct data, correct output), negative test cases
(broken or missing data, proper handling), exception test cases
(exceptions are thrown and caught properly).

· Can you change the value of a variable while debugging a C#
application?
Yes, if you are debugging via Visual Studio.NET, just go to immediate
window.

· What's the implicit name of the parameter that gets passed into the
class' set method?
Value, and it's datatype depends on whatever variable we're changing.

· How do you inherit from a class in C#?
Place a colon and then the name of the base class. Notice that it's
double colon in C++.

· Does C# support multiple inheritance?
No, use interfaces instead.

· When you inherit a protected class-level variable, who is it
available to?
Derived Classes.

· What's the top .NET class that everything is derived from?
System.Object.

· How's method overriding different from overloading?
When overriding, you change the method behavior for a derived class.
Overloading simply involves having a method with the same name within
the class.

· What does the keyword virtual mean in the method definition?
The method can be over-ridden.

· Can you declare the override method static while the original
method is non-static?
No, you can't, the signature of the virtual method must remain the
same, and only the keyword virtual is changed to keyword override.

· Can you override private virtual methods?
No, moreover, you cannot access private methods in inherited classes,
have to be protected in the base class to allow any sort of access.

· Can you prevent your class from being inherited and becoming a base
class for some other classes?
Yes, that's what keyword sealed in the class definition is for. The
developer trying to derive from your class will get a message: cannot
inherit from Sealed class WhateverBaseClassName. It's the same concept
as final class in Java.

· Can you allow class to be inherited, but prevent the method from
being over-ridden?
Yes, just leave the class public and make the method sealed.

· Why can't you specify the accessibility modifier for methods inside
the interface?
They all must be public. Therefore, to prevent you from getting the
false impression that you have any freedom of choice, you are not
allowed to specify any accessibility, it's public by default.

· Can you inherit multiple interfaces? And if they have conflicting
method names?
Yes, why not.

It's up to you to implement the method inside your own class, so
implementation is left entirely up to you. This might cause a problem
on a higher-level scale if similarly named methods from different
interfaces expect different data, but as far as compiler cares you're
okay.

· What's the difference between an interface and abstract class?
In the interface all methods must be abstract, in the abstract class
some methods can be concrete. In the interface no accessibility
modifiers are allowed, which is ok in abstract classes.

· How can you overload a method?
By having Different parameter data types.
By having different number of parameters.
By having different order of parameters.

· If a base class has a bunch of overloaded constructors, and an
inherited class has another bunch of overloaded constructors, can you
enforce a call from an inherited constructor to an arbitrary base
constructor?
Yes, just place a colon, and then keyword base (parameter list to
invoke the appropriate constructor) in the overloaded constructor
definition inside the inherited class.

· What's the difference between System.String and
System.StringBuilder classes?
System.String is immutable, System.StringBuilder was designed with the
purpose of having a mutable string where a variety of operations can be
performed.

· Does C# support multiple-inheritance?
No, use interfaces instead.

· When you inherit a protected class-level variable, who is it
available to?
The derived class.

· Are private class-level variables inherited?
Yes, but they are not accessible. Although they are not visible or
accessible via the class interface, they are inherited.

· Describe the accessibility modifier "protected internal".
It is available to derived classes and classes within the same Assembly
(and naturally from the base class it's declared in).

· What's the top .NET class that everything is derived from?
System.Object.

· What's the advantage of using System.Text.StringBuilder over
System.String?
StringBuilder is more efficient in cases where there is a large amount
of string manipulation. Strings are immutable, so each time it's being
operated on, a new instance is created.

· Can you store multiple data types in System.Array?
No.

· What's the .NET class that allows the retrieval of a data element
using a unique key?
HashTable.

· Will the finally block get executed if an exception has not
occurred?
Yes.

· What's an abstract class?
Abstract class is a class that cannot be instantiated. An abstract
class is a class that must be inherited and have the methods
overridden. An abstract class is essentially a blueprint for a class
without any implementation.

· When do you absolutely have to declare a class as abstract?
1. When at least one of the methods in the class is abstract.
2. When the class itself is inherited from an abstract class,
but not all base abstract
methods have been overridden.

· What's an interface?
It's an abstract class with public abstract methods all of which must
be implemented in the inherited classes.

· Why can't you specify the accessibility modifier for methods inside
the interface?
They all must be public. Therefore, to prevent you from getting the
false impression that you have any freedom of choice, you are not
allowed to specify any accessibility, it's public by default.

· What's the difference between an interface and abstract class?
In an interface class, all methods must be abstract. In an abstract
class some methods can be concrete. In an interface class, no
accessibility modifiers are allowed, which is ok in an abstract class.

· How is method overriding different from method overloading?
When overriding a method, you change the behavior of the method for the
derived class. Overloading a method simply involves having another
method with the same name within the class.

· Can you declare an override method to be static if the original
method is non-static?
No. The signature of the virtual method must remain the same, only the
keyword virtual is changed to keyword override.

· Can you override private virtual methods?
No. Private methods are not accessible outside the class.

· Can you write a class without specifying namespace? Which namespace
does it belong to by default?
Yes, you can, then the class belongs to global namespace which has no
name. For commercial products, naturally, you wouldn't want global
namespace.

· What is a formatter?
A formatter is an object that is responsible for encoding and
serializing data into messages on one end, and deserializing and
decoding messages into data on the other end.

· Different b/w .NET & J2EE?
Differences between J2EE and the .NET Platform
Vendor Neutrality
The .NET platform is not vendor neutral, it is tied to the Microsoft
operating systems. But neither are any of the J2EE implementations
Many companies buy into J2EE believing that it will give them vendor
neutrality. And, in fact, this is a stated goal of Sun's vision:
A wide variety of J2EE product configurations and implementations, all
of which meet the requirements of this specification, are possible. A
portable J2EE application will function correctly when successfully
deployed in any of these products. (ref : Java 2 Platform Enterprise
Edition Specification, v1.3, page 2-7 available at
http://java.sun.com/j2ee/)
Overall Maturity
Given that the .NET platform has a three year lead over J2EE, it should
be no surprise to learn that the .NET platform is far more mature than
the J2EE platform. Whereas we have high volume highly reliable web
sites using .NET technologies (NASDAQ and Dell being among many
examples)
Interoperability and Web Services
The .NET platform eCollaboration model is, as I have discussed at
length, based on the UDDI and SOAP standards. These standards are
widely supported by more than 100 companies. Microsoft, along with IBM
and Ariba, are the leaders in this area. Sun is a member of the UDDI
consortium and recognizes the importance of the UDDI standards. In a
recent press release, Sun's George Paolini, Vice President for the Java
Community Development, says: "Sun has always worked to help establish
and support open, standards-based technologies that facilitate the
growth of network-based applications, and we see UDDI as an important
project to establish a registry framework for business-to-business
e-commerce". But while Sun publicly says it believes in the UDDI
standards, in reality, Sun has done nothing whatsoever to incorporate
any of the UDDI standards into J2EE.
Scalability
Typical Comparision w.r.t Systems and their costs
J2EE
Company System Total Sys.
Cost
Bull Escala T610 c/s
16,785 $1,980,179
IBM RS/6000 Enterprise Server F80
16,785 $2,026,681
Bull Escala EPC810 c/s
33,375 $3,037,499
IBM RS/6000 Enterprise Server M80
33,375 $3,097,055
Bull Escala EPC2450
110,403 $9,563,263
IBM IBM eServer pSeries 680 Model 7017-S85 110,403
$9,560,594

.NET platform systems
Company System Total Sys.
Cost
Dell PowerEdge 4400
16,263 $273,487
Compaq ProLiant ML-570-6/700-3P 20,207
$201,717
Dell PowerEdge 6400
30,231 $334,626
IBM Netfinity 7600 c/s
32,377 $443,463
Compaq ProLiant 8500-X550-64P
161,720 $3,534,272
Compaq ProLiant 8500-X700-64P
179,658 $3,546,582
Compaq ProLiant 8500-X550-96P
229,914 $5,305,571
Compaq ProLiant 8500-X700-96P
262,244 $5,305,571
Compaq ProLiant 8500-700-192P
505,303 $10,003,826
Framework Support
The .NET platform includes such an eCommerce framework called Commerce
Server. At this point, there is no equivalent vendor-neutral framework
in the J2EE space. With J2EE, you should assume that you will be
building your new eCommerce solution from scratch
Moreover, no matter what [J2EE] vendor you choose, if you expect a
component framework that will allow you to quickly field complete
e-business applications, you are in for a frustrating experience
Language
In the language arena, the choice is about as simple as it gets. J2EE
supports Java, and only Java. It will not support any other language in
the foreseeable future. The .NET platform supports every language
except Java (although it does support a language that is syntactically
and functionally equivalent to Java, C#). In fact, given the importance
of the .NET platform as a language independent vehicle, it is likely
that any language that comes out in the near future will include
support for the .NET platform.
Some companies are under the impression that J2EE supports other
languages. Although both IBM's WebSphere and BEA's WebLogic support
other languages, neither does it through their J2EE technology. There
are only two official ways in the J2EE platform to access other
languages, one through the Java Native Interface and the other through
CORBA interoperability. Sun recommends the later approach. As Sun's
Distinguished Scientist and Java Architect Rick Cattell said in a
recent interview.
Portability
The reason that operating system portability is a possibility with J2EE
is not so much because of any inherent portability of J2EE, as it is
that most of the J2EE vendors support multiple operating systems.
Therefore as long as one sticks with a given J2EE vendor and a given
database vendor, moving from one operating system to another should be
possible. This is probably the single most important benefit in favor
of J2EE over the .NET platform, which is limited to the Windows
operating system. It is worth noting, however, that Microsoft has
submitted the specifications for C# and a subset of the .NET Framework
(called the common language infrastructure) to ECMA, the group that
standardizes JavaScript.
J2EE offers an acceptable solution to ISVs when the product must be
marketed to non-Windows customers, particularly when the J2EE platform
itself can be bundled with the ISV's product as an integrated offering.

If the primary customer base for the ISV is Windows customers, then
the .NET platform should be chosen. It will provide much better
performance at a much lower cost.

Client device independence
The major difference being that with Java, it is the presentation tier
programmer that determines the ultimate HTML that will be delivered to
the client, and with .NET, it is a Visual Studio.NET control.
This Java approach has three problems. First, it requires a lot of code
on the presentation tier, since every possible thin client system
requires a different code path. Second, it is very difficult to test
the code with every possible thin client system. Third, it is very
difficult to add new thin clients to an existing application, since to
do so involves searching through, and modifying a tremendous amount of
presentation tier logic.
The .NET Framework approach is to write device independent code that
interacts with visual controls. It is the control, not the programmer,
that is responsible for determining what HTML to deliver, based on the
capabilities of the client device.. In the .NET Framework model, one
can forget that such a thing as HTML even exists!
Conclusion
Sun's J2EE vision is based on a family of specifications that can be
implemented by many vendors. It is open in the sense that any company
can license and implement the technology, but closed in the sense that
it is controlled by a single vendor, and a self contained architectural
island with very limited ability to interact outside of itself. One of
J2EE's major disadvantages is that the choice of the platform dictates
the use of a single programming language, and a programming language
that is not well suited for most businesses. One of J2EE's major
advantages is that most of the J2EE vendors do offer operating system
portability.
Microsoft's .NET platform vision is a family of products rather than
specifications, with specifications used primarily to define points of
interoperability. The major disadvantage of this approach is that if is
limited to the Windows platform, so applications written for the .NET
platform can only be run on .NET platforms. Their are several important
advantages to the .NET platform:
* The cost of developing applications is much lower, since standard
business languages can be used and device independent presentation tier
logic can be written.
* The cost of running applications is much lower, since commodity
hardware platforms (at 1/5 the cost of their Unix counterparts) can be
used.
* The ability to scale up is much greater, with the proved ability to
support at least ten times the number of clients any J2EE platform has
shown itself able to support.
* Interoperability is much stronger, with industry standard
eCollaboration built into the platform.
· What are the Main Features of .NET platform?
Features of .NET Platform are :-
Common Language Runtime
Explains the features and benefits of the common language runtime, a
run-time environment that manages the execution of code and provides
services that simplify the development process.
Assemblies
Defines the concept of assemblies, which are collections of types and
resources that form logical units of functionality. Assemblies are the
fundamental units of deployment, version control, reuse, activation
scoping, and security permissions.
Application Domains
Explains how to use application domains to provide isolation between
applications.
Runtime Hosts
Describes the runtime hosts supported by the .NET Framework, including
ASP.NET, Internet Explorer, and shell executables.
Common Type System
Identifies the types supported by the common language runtime.
Metadata and Self-Describing Components
Explains how the .NET Framework simplifies component interoperation by
allowing compilers to emit additional declarative information, or
metadata, into all modules and assemblies.
Cross-Language Interoperability
Explains how managed objects created in different programming languages
can interact with one another.
..NET Framework Security
Describes mechanisms for protecting resources and code from
unauthorized code and unauthorized users.
..NET Framework Class Library
Introduces the library of types provided by the .NET Framework, which
expedites and optimizes the development process and gives you access to
system functionality.
· What is the use of JIT ?
JIT (Just - In - Time) is a compiler which converts MSIL code to Native
Code (ie.. CPU-specific code that runs on the same computer
architecture).
Because the common language runtime supplies a JIT compiler for each
supported CPU architecture, developers can write a set of MSIL that can
be JIT-compiled and run on computers with different architectures.
However, your managed code will run only on a specific operating system
if it calls platform-specific native APIs, or a platform-specific class
library.
JIT compilation takes into account the fact that some code might never
get called during execution. Rather than using time and memory to
convert all the MSIL in a portable executable (PE) file to native code,
it converts the MSIL as needed during execution and stores the
resulting native code so that it is accessible for subsequent calls.
The loader creates and attaches a stub to each of a type's methods when
the type is loaded. On the initial call to the method, the stub passes
control to the JIT compiler, which converts the MSIL for that method
into native code and modifies the stub to direct execution to the
location of the native code. Subsequent calls of the JIT-compiled
method proceed directly to the native code that was previously
generated, reducing the time it takes to JIT-compile and run the code.
· What meant of assembly & global assembly cache (gac) & Meta data.
Assembly :-- An assembly is the primary building block of a .NET based
application. It is a collection of functionality that is built,
versioned, and deployed as a single implementation unit (as one or more
files). All managed types and resources are marked either as accessible
only within their implementation unit, or as accessible by code outside
that unit. It overcomes the problem of 'dll Hell'.The .NET Framework
uses assemblies as the fundamental unit for several purposes:
1. Security
2. Type Identity
3. Reference Scope
4. Versioning
5. Deployment
Global Assembly Cache :-- Assemblies can be shared among multiple
applications on the machine by registering them in global Assembly
cache(GAC). GAC is a machine wide a local cache of assemblies
maintained by the .NET Framework. We can register the assembly to
global assembly cache by using gacutil command.

We can Navigate to the GAC directory, C:\winnt\Assembly in explore. In
the tools menu select the cache properties; in the windows displayed
you can set the memory limit in MB used by the GAC

MetaData :--Assemblies have Manifests. This Manifest contains Metadata
information of the Module/Assembly as well as it contains detailed
Metadata of other assemblies/modules references (exported). It's the
Assembly Manifest which differentiates between an Assembly and a
Module.

· What are the mobile devices supported by .net platform
The Microsoft .NET Compact Framework is designed to run on mobile
devices such as mobile phones, Personal Digital Assistants (PDAs), and
embedded devices. The easiest way to develop and test a Smart Device
Application is to use an emulator.

These devices are divided into two main divisions:
1) Those that are directly supported by .NET (Pocket PCs, i-Mode
phones, and WAP devices)
2) Those that are not (Palm OS and J2ME-powered devices).

· What is GUID , why we use it and where?
GUID :-- GUID is Short form of Globally Unique Identifier, a unique
128-bit number that is produced by the Windows OS or by some Windows
applications to identify a particular component, application, file,
database entry, and/or user. For instance, a Web site may generate a
GUID and assign it to a user's browser to record and track the session.
A GUID is also used in a Windows registry to identify COM DLLs. Knowing
where to look in the registry and having the correct GUID yields a lot
information about a COM object (i.e., information in the type library,
its physical location, etc.). Windows also identifies user accounts by
a username (computer/domain and username) and assigns it a GUID. Some
database administrators even will use GUIDs as primary key values in
databases.
GUIDs can be created in a number of ways, but usually they are a
combination of a few unique settings based on specific point in time
(e.g., an IP address, network MAC address, clock date/time, etc.).

· Describe the difference between inline and code behind - which is
best in a loosely coupled solution
ASP.NET supports two modes of page development: Page logic code that is
written inside runat="server"blocks within an .aspx file and
dynamically compiled the first time the page is requested on the
server. Page logic code that is written within an external class that
is compiled prior to deployment on a server and linked ""behind"" the
..aspx file at run time.

· Whats MSIL, and why should my developers need an appreciation of it
if at all?
When compiling the source code to managed code, the compiler translates
the source into Microsoft intermediate language (MSIL). This is a
CPU-independent set of instructions that can efficiently be converted
to native code. Microsoft intermediate language (MSIL) is a translation
used as the output of a number of compilers. It is the input to a
just-in-time (JIT) compiler. The Common Language Runtime includes a JIT
compiler for the conversion of MSIL to native code.

Before Microsoft Intermediate Language (MSIL) can be executed it, must
be converted by the .NET Framework just-in-time (JIT) compiler to
native code. This is CPU-specific code that runs on the same computer
architecture as the JIT compiler. Rather than using time and memory to
convert all of the MSIL in a portable executable (PE) file to native
code. It converts the MSIL as needed whilst executing, then caches the
resulting native code so its accessible for any subsequent calls.

· How many .NET languages can a single .NET DLL contain?
One
· What type of code (server or client) is found in a Code-Behind
class?
Server
· What is an assembly?
Assemblies are the building blocks of .NET Framework applications; they
form the fundamental unit of deployment, version control, reuse,
activation scoping, and security permissions. An assembly is a
collection of types and resources that are built to work together and
form a logical unit of functionality. An assembly provides the common
language runtime with the information it needs to be aware of type
implementations. To the runtime, a type does not exist outside the
context of an assembly.
· How many classes can a single .NET DLL contain?
Unlimited.
· What is the difference between string and String ?
No difference
· What is manifest?
It is the metadata that describes the assemblies.
· What is metadata?
Metadata is machine-readable information about a resource, or ""data
about data."" Such information might include details on content,
format, size, or other characteristics of a data
source. In .NET, metadata includes type definitions, version
information, external assembly references, and other standardized
information.
· What are the types of assemblies?
There are four types of assemblies in .NET:
Static assemblies
These are the .NET PE files that you create at compile time.
Dynamic assemblies
These are PE-formatted, in-memory assemblies that you dynamically
create at runtime using the classes in the System.Reflection.Emit
namespace.
Private assemblies
These are static assemblies used by a specific application.
Public or shared assemblies
These are static assemblies that must have a unique shared name and can
be used by any application.
An application uses a private assembly by referring to the assembly
using a static path or through an XML-based application configuration
file. While the CLR doesn't enforce versioning policies-checking
whether the correct version is used-for private assemblies, it ensures
that an
application uses the correct shared assemblies with which the
application was built. Thus, an application uses a specific shared
assembly by referring to the specific shared assembly, and the CLR
ensures that the correct version is loaded at runtime.
In .NET, an assembly is the smallest unit to which you can associate a
version number;
· What are delegates?where are they used ?
A delegate defines a reference type that can be used to encapsulate a
method with a specific signature. A delegate instance encapsulates a
static or an instance method. Delegates are roughly similar to function
pointers in C++; however, delegates are type-safe and secure.

· When do you use virutal keyword?.
When we need to override a method of the base class in the sub class,
then we give the virtual keyword in the base class method. This makes
the method in the base class to be overridable. Methods, properties,
and indexers can be virtual, which means that their implementation can
be overridden in derived classes.

· What are class access modifiers ?
Access modifiers are keywords used to specify the declared
accessibility of a member or a type. This section introduces the four
access modifiers:
· Public - Access is not restricted.
· Protected - Access is limited to the containing class or types
derived from the containing class.
· Internal - Access is limited to the current assembly.
· Protected inertnal - Access is limited to the current assembly or
types derived · from the containing class.
· Private - Access is limited to the containing type.

· What Is Boxing And Unboxing?
Boxing :- Boxing is an implicit conversion of a value type to the type
object type
Eg:-
Consider the following declaration of a value-type variable:
int i = 123;
object o = (object) i;
Boxing Conversion
UnBoxing :- Unboxing is an explicit conversion from the type object to
a value type
Eg:
int i = 123; // A value type
object box = i; // Boxing
int j = (int)box; // Unboxing
· What is Value type and refernce type in .Net?.
Value Type : A variable of a value type always contains a value of that
type. The assignment to a variable of a value type creates a copy of
the assigned value, while the assignment to a variable of a reference
type creates a copy of the reference but not of the referenced object.
The value types consist of two main categories:
* Stuct Type
* Enumeration Type
Reference Type :Variables of reference types, referred to as objects,
store references to the actual data. This section introduces the
following keywords used to declare reference types:
* Class
* Interface
* Delegate
This section also introduces the following built-in reference types:
* object
* string
· What is the difference between structures and enumeration?.
Unlike classes, structs are value types and do not require heap
allocation. A variable of a struct type directly contains the data of
the struct, whereas a variable of a class type contains a reference to
the data. They are derived from System.ValueType class.
Enum->An enum type is a distinct type that declares a set of named
constants.They are strongly typed constants. They are unique types
that allow to declare symbolic names to integral values. Enums are
value types, which means they contain their own value, can't inherit or
be inherited from and assignment copies the value of one enum to
another.
public enum Grade
{
A,
B,
C
}
· What is namespaces?
Namespace is a logical naming scheme for group related types.Some class
types that logically belong together they can be put into a common
namespace. They prevent namespace collisions and they provide scoping.
They are imported as "using" in C# or "Imports" in Visual Basic. It
seems as if these directives specify a particular assembly, but they
don't. A namespace can span multiple assemblies, and an assembly can
define multiple namespaces. When the compiler needs the definition for
a class type, it tracks through each of the different imported
namespaces to the type name and searches each referenced assembly until
it is found.
Namespaces can be nested. This is very similar to packages in Java as
far as scoping is concerned.
· How do you create shared assemblies?
Just look through the definition of Assemblies..
* An Assembly is a logical unit of code
* Assembly physically exist as DLLs or EXEs
* One assembly can contain one or more files
* The constituent files can include any file types like image files,
text files etc. along with DLLs or EXEs
* When you compile your source code by default the exe/dll generated
is actually an assembly
* Unless your code is bundled as assembly it can not be used in any
other application
* When you talk about version of a component you are actually
talking about version of the assembly to which the component belongs.
* Every assembly file contains information about itself. This
information is called as Assembly Manifest.
Following steps are involved in creating shared assemblies :
* Create your DLL/EXE source code
* Generate unique assembly name using SN utility
* Sign your DLL/EXE with the private key by modifying AssemblyInfo
file
* Compile your DLL/EXE
* Place the resultant DLL/EXE in global assembly cache using AL
utility

· What is global assembly cache?
Each computer where the common language runtime is installed has a
machine-wide code cache called the global assembly cache. The global
assembly cache stores assemblies specifically designated to be shared
by several applications on the computer.
There are several ways to deploy an assembly into the global assembly
cache:
1. Use an installer designed to work with the global assembly cache.
This is the preferred option for installing assemblies into the global
assembly cache.
2. Use a developer tool called the Global Assembly Cache tool
(Gacutil.exe), provided by the .NET Framework SDK.
3. Use Windows Explorer to drag assemblies into the cache.

· What is MSIL?
When compiling to managed code, the compiler translates your source
code into Microsoft intermediate language (MSIL), which is a
CPU-independent set of instructions that can be efficiently converted
to native code. MSIL includes instructions for loading, storing,
initializing, and calling methods on objects, as well as instructions
for arithmetic and logical operations, control flow, direct memory
access, exception handling, and other operations. Before code can be
run, MSIL must be converted to CPU-specific code, usually by a
just-in-time (JIT) compiler. Because the common language runtime
supplies one or more JIT compilers for each computer architecture it
supports, the same set of MSIL can be JIT-compiled and run on any
supported architecture.
When a compiler produces MSIL, it also produces metadata. Metadata
describes the types in your code, including the definition of each
type, the signatures of each type's members, the members that your code
references, and other data that the runtime uses at execution time. The
MSIL and metadata are contained in a portable executable (PE) file that
is based on and extends the published Microsoft PE and common object
file format (COFF) used historically for executable content. This file
format, which accommodates MSIL or native code as well as metadata,
enables the operating system to recognize common language runtime
images. The presence of metadata in the file along with the MSIL
enables your code to describe itself, which means that there is no need
for type libraries or Interface Definition Language (IDL). The runtime
locates and extracts the metadata from the file as needed during
execution.

· What is Jit compilers?.how many are available in clr?
Just-In-Time compiler- it converts the language that you write in .Net
into machine language that a computer can understand. there are tqo
types of JITs one is memory optimized & other is performace
optimized.

· What is tracing?Where it used. Explain few methods available
Tracing refers to collecting information about the application while it
is running. You use tracing information to troubleshoot an
application.
Tracing allows us to observe and correct programming errors. Tracing
enables you to record information in various log files about the errors
that might occur at run time. You can analyze these log files to find
the cause of the errors.
In .NET we have objects called Trace Listeners. A listener is an object
that receives the trace output and outputs it somewhere; that somewhere
could be a window in your development environment, a file on your hard
drive, a Windows Event log, a SQL Server or Oracle database, or any
other customized data store.
The System.Diagnostics namespace provides the interfaces, classes,
enumerations and structures that are used for tracing The
System.Diagnostics namespace provides two classes named Trace and Debug
that are used for writing errors and application execution information
in logs.
All Trace Listeners have the following functions. Functionality of
these functions is same except that the target media for the tracing
output is determined by the Trace Listener.
Method Name
Result Fail Outputs the specified text with the Call Stack.
Write Outputs the specified text.
WriteLine Outputs the specified text and a carriage return.
Flush Flushes the output buffer to the target media.
Close Closes the output stream in order to not receive the
tracing/debugging output.
· How to set the debug mode?
Debug Mode for ASP.NET applications - To set ASP.NET appplication in
debugging mode, edit the application's web.config and assign the
"debug" attribute in < compilation section to "true" as show below:
< configuration >
< system.web >
< compilation defaultLanguage="vb" debug="true" / >
.....
....
...
< / configuration >
This case-sensitive attribute 'debug tells ASP.NET to generate symbols
for dynamically generated files and enables the debugger to attach to
the ASP.NET application. ASP.NET will detect this change automatically,
without the need to restart the server. Debug Mode for ASP.NET
Webservices - Debugging an XML Web service created with ASP.NET is
similar to the debugging an ASP.NET Web application.
· What is the property available to check if the page posted or not?
The Page_Load event handler in the page checks for IsPostBack property
value, to ascertain whether the page is posted. The Page.IsPostBack
gets a value indicating whether the page is being loaded in response to
the client postback, or it is for the first time. The value of
Page.IsPostBack is True, if the page is being loaded in response to the
client postback; while its value is False, when the page is loaded for
the first time. The Page.IsPostBack property facilitates execution of
certain routine in Page_Load, only once (for e.g. in Page load, we need
to set default value in controls, when page is loaded for the first
time. On post back, we check for true value for IsPostback value and
then invoke server-side code to
update data).

· Which are the abstract classes available under system.xml
namespace?
The System.XML namespace provides XML related processing ability in
..NET framework. XmlReader and XMLWriter are the two abstract classes at
the core of .NET Framework XML classes:
1. XmlReader provides a fast, forward-only, read-only cursor for
processing an XML document stream.
2. XmlWriter provides an interface for producing XML document streams
that conform to the W3C's XML standards.
Both XmlReader and XmlWriter are abstract base classes, which define
the functionality that all derived classes must support.
· Is it possible to use multipe inheritance in .net?
Multiple Inheritance is an ability to inherit from more than one base
class i.e. ability of a class to have more than one superclass, by
inheriting from different sources and thus combine separately-defined
behaviors in a single class. There are two types of multiple
inheritance: multiple type/interface inheritance and multiple
implementation inheritance. C# & VB.NET supports only multiple
type/interface inheritance, i.e.
you can derive an class/interface from multiple interfaces. There is no
support for multiple implementation inheritance in .NET. That means a
class can only derived from one class.

· What are the derived classes from xmlReader and xmlWriter?
Both XmlReader and XmlWriter are abstract base classes, which define
the functionality that all derived classes must support.
There are three concrete implementations of XmlReader:
1.XmlTextReader
2.XmlNodeReader
3.XmlValidatingReader
There are two concrete implementations of XmlWriter:
1.XmlTextWriter
2.XmlNodeWriter
XmlTextReader and XmlTextWriter support reading data to/from text-based
stream, while XmlNodeReader and XmlNodeWriter are designed for working
with in-memory DOM tree structure. The custom readers and writers can
also be developed to extend the built-in functionality of XmlReader and
XmlWriter.
· What is managed and unmanaged code?
The .NET framework provides several core run-time services to the
programs that run within it - for example exception handling and
security. For these services to work, the code must provide a minimum
level of information to the runtime. i.e., code executing under the
control of the CLR is called managed code. For example, any code
written in C# or Visual Basic .NET is managed code.
Code that runs outside the CLR is referred to as "unmanaged code." COM
components, ActiveX components, and Win32 API functions are examples of
unmanaged code.
· How you deploy .NET assemblies?
One way is simply use xcopy. others are use and the setup projects in
..net. and one more way is use of no touch deployment.

· What is Globalizationa and Localization ?
Globalization is the process of creating an application that meets the
needs of users from multiple cultures. It includes using the correct
currency, date and time format, calendar, writing direction, sorting
rules, and other issues. Accommodating these cultural differences in an
application is called localization.Using classes of
System.Globalization namespace, you can set application's current
culture.
This can be achieved by using any of the following 3 approaches.
1. Detect and redirect
2. Run-time adjustment
3. Using Satellite assemblies.
· What are Resource Files ? How are they used in .NET?
Resource files are the files containing data that is logically deployed
with an application.These files can contain data in a number of formats
including strings, images and persisted objects. It has the main
advantage of If we store data in these files then we don't need to
compile these if the data get changed. In .NET we basically require
them storing culture specific informations by localizing application's
resources. You can deploy your resources using satellite assemblies.

· Difference between Dispose and Finallize method?
Finalize method is used to free the memory used by some unmanaged
resources like window handles (HWND). It's similar to the destructor
syntax in C#. The GC calls this method when it founds no more
references to the object. But, In some cases we may need release the
memory used by the resources explicitely.To release the memory
explicitly we need to implement the Dispose method of IDisposable
interface.

· What is encapsulation ?
Encapsulation is the ability to hide the internal workings of an
object's behavior and its data. For instance, let's say you have a
object named Bike and this object has a method named start(). When you
create an instance of a Bike object and call its start() method you are
not worried about what happens to accomplish this, you just want to
make sure the state of the bike is changed to 'running' afterwards.
This kind of behavior hiding is encapsulation and it makes programming
much easier.

· How can you prevent your class to be inherated further?
By setting Sealed - Key word
public sealed class Planet
{
//code goes here
}
class Moon:Planet
{
//Not allowed as base class is sealed
}
· What is GUID and why we need to use it and in what condition? How
this is created.
A GUID is a 128-bit integer (16 bytes) that can be used across all
computers and networks wherever a unique identifier is required. Such
an identifier has a very low probability of being duplicated. Visual
Studio .NET IDE has a utility under the tools menu to generate GUIDs.

· Why do you need to serialize.?
We need to serialize the object,if you want to pass object from one
computer/application domain to another.Process of converting complex
objects into stream of bytes that can be persisted or
transported.Namespace for serialization is
System.Runtime.Serialization.The ISerializable interface allows you to
make any class Serializable..NET framework features 2 serializing
method.
1.Binary Serialization 2.XML Serialization

· What is inline schema, how does it works?
Schemas can be included inside of XML file is called Inline
Schemas.This is useful when it is inconvenient to physically seprate
the schema and the XML document.A schema is an XML document that
defines the structure, constraints, data types, and relationships of
the elements that constitute the data contained inside the XML
document or in another XML document.Schema can be an external file
which uses the XSD or XDR extension called external schema. Inline
schema can take place even when validation is turned off.

· Describe the advantages of writing a managed code application
instead of unmanaged one. What's involved in certain piece of code
being managed?
"Advantage includes automatic garbage collection,memory
management,security,type checking,versioning
Managed code is compiled for the .NET run-time environment. It runs in
the Common Language Runtime (CLR), which is the heart of the .NET
Framework. The CLR provides services such as security, memory
management, and cross-language integration. Managed applications
written to take advantage of the features of the CLR perform more
efficiently and safely, and take better advantage of developers
existing expertise in languages that support the .NET Framework.
Unmanaged code includes all code written before the .NET Framework was
introduced-this includes code written to use COM, native Win32, and
Visual Basic 6. Because it does not run inside the .NET environment,
unmanaged code cannot make use of any .NET managed facilities."
· What are multicast delegates? Give an example?
Delegate that can have more than one element in its invocation List.
using System;
namespace SampleMultiCastDelegate
{
class MultiCast
{
public delegate string strMultiCast(string s);
}
}

MainClass defines the static methods having same signature as delegate.
using System;
namespace SampleMultiCastDelegate
{

public class MainClass
{
public MainClass()
{
}
public static string Jump(string s)
{
Console.WriteLine("Jump");
return String.Empty;
}
public static string Run(string s)
{
Console.WriteLine("Run");
return String.Empty;
}
public static string Walk(string s)
{
Console.WriteLine("Walk");
return String.Empty;
}
}
}
The Main class:
using System;
using System.Threading;
namespace SampleMultiCastDelegate
{

public class MainMultiCastDelegate
{
public static void Main()
{
MultiCast.strMultiCast Run,Walk,Jump;
MultiCast.strMultiCast myDelegate;
///here mydelegate used the Combine method of
System.MulticastDelegate
///and the delegates combine

myDelegate=(MultiCast.strMultiCast)System.Delegate .Combine(Run,Walk);

}
}
}
· Can a nested object be used in Serialization ?
Yes. If a class that is to be serialized contains references to objects
of other classes, and if those classes have been marked as
serializable, then their objects are serialized too.

· Difference between int and int32 ?
Both are same. System.Int32 is a .NET class. Int is an alias name for
System.Int32.

· Describe the difference between a Thread and a Process?
A Process is an instance of an running application. And a thread is the
Execution stream of the Process. A process can have multiple Thread.
When a process starts a specific memory area is allocated to it. When
there is multiple thread in a process, each thread gets a memory for
storing the variables in it and plus they can access to the global
variables which is common for all the thread. Eg.A Microsoft Word is a
Application. When you open a word file,an instance of the Word starts
and a process is allocated to this instance which has one thread.

· What is the difference between an EXE and a DLL?
You can create an objects of Dll but not of the EXE.
Dll is an In-Process Component whereas EXE is an OUt-Process Component.
Exe is for single use whereas you can use Dll for multiple use.
Exe can be started as standalone where dll cannot be.

· What is strong-typing versus weak-typing? Which is preferred? Why?
Strong typing implies that the types of variables involved in
operations are associated to the variable, checked at compile-time, and
require explicit conversion; weak typing implies that they are
associated to the value, checked at run-time, and are implicitly
converted as required. (Which is preferred is a disputable point, but I
personally prefer strong typing because I like my errors to be found as
soon as possible.)
· What is a PID? How is it useful when troubleshooting a system?
PID is the process Id of the application in Windows. Whenever a process
starts running in the Windows environment, it is associated with an
individual process Id or PID.
The PID (Process ID) a unique number for each item on the Process Tab,
Image Name list. How do you get the PID to appear? In Task Manger,
select the View menu, then select columns and check PID (Process
Identifier).
In Linux, PID is used to debug a process explicitly. However we cannot
do this in a windows environment.
Microsoft has launched a SDK called as Microsoft Operations Management
(MOM). This uses the PID to find out which dll's have been loaded by
a process in the memory. This is essentially helpful in situations
where the Process which has a memory leak is to be traced to a erring
dll. Personally I have never used a PID, our Windows debugger does the
things required to find out.
· What is the GAC? What problem does it solve?
Each computer where the common language runtime is installed has a
machine-wide code cache called the global assembly cache. The global
assembly cache stores assemblies that are to be shared by several
applications on the computer. This area is typically the folder under
windows or winnt in the machine.
All the assemblies that need to be shared across applications need to
be done through the Global assembly Cache only. However it is not
necessary to install assemblies into the global assembly cache to make
them accessible to COM interop or unmanaged code.
There are several ways to deploy an assembly into the global assembly
cache:
1. Use an installer designed to work with the global assembly cache.
This is the preferred option for installing assemblies into the global
assembly cache.
2. Use a developer tool called the Global Assembly Cache tool
(Gacutil.exe), provided by the .NET Framework SDK.
3. Use Windows Explorer to drag assemblies into the cache.
GAC solves the problem of DLL Hell and DLL versioning. Unlike earlier
situations, GAC can hold two assemblies of the same name but different
version. This ensures that the applications which access a particular
assembly continue to access the same assembly even if another version
of that assembly is installed on that machine.
· Describe what an Interface is and how it's different from a
Class.
An interface is a structure of code which is similar to a class. An
interface is a prototype for a class and is useful from a logical
design perspective. Interfaces provide a means to define the protocols
for a class without worrying about the implementation details. The
syntax for creating interfaces follows:

interface Identifier {
InterfaceBody
}
Identifier is the name of the interface and InterfaceBody refers to the
abstract methods and static final variables that make up the interface.
Because it is assumed that all the methods in an interface are
abstract, it isn't necessary to use the abstract keyword
An interface is a description of some of the members available from a
class. In practice, the syntax typically looks similar to a class
definition, except that there's no code defined for the methods -
just their name, the arguments passed and the type of the value
returned.
So what good is it? None by itself. But you create an interface so that
classes will implement it.
But what does it mean to implement an interface. The interface acts as
a contract or promise. If a class implements an interface, then it must
have the properties and methods of the interface defined in the class.
This is enforced by the compiler.
Broadly the differentiators between classes and interfaces is as
follows
· Interface should not have any implementation.
· Interface can not create any instance.
· Interface should provide high level abstraction from the
implementation.
· Interface can have multiple inheritances.
· Default access level of the interface is public.
· What is the difference between XML Web Services using ASMX and .NET
Remoting using SOAP?
ASP.NET Web services and .NET Remoting provide a full suite of design
options for cross-process and cross-plaform communication in
distributed applications. In general, ASP.NET Web services provide the
highest levels of interoperability with full support for WSDL and SOAP
over HTTP, while .NET Remoting is designed for common language runtime
type-system fidelity and supports additional data format and
communication channels. Hence if we looking cross-platform
communication than web services is the choice coz for .NET remoting
..Net framework is requried which may or may not present for the other
platform.
Serialization and Metadata
ASP.NET Web services rely on the System.Xml.Serialization.XmlSerializer
class to marshal data to and from SOAP messages at runtime. For
metadata, they generate WSDL and XSD definitions that describe what
their messages contain. The reliance on pure WSDL and XSD makes ASP.NET
Web services metadata portable; it expresses data structures in a way
that other Web service toolkits on different platforms and with
different programming models can understand. In some cases, this
imposes constraints on the types you can expose from a Web
service-XmlSerializer will only marshal things that can be expressed
in XSD. Specifically, XmlSerializer will not marshal object graphs and
it has limited support for container types.
..NET Remoting relies on the pluggable implementations of the IFormatter
interface used by the System.Runtime.Serialization engine to marshal
data to and from messages. There are two standard formatters,
System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter and
System.Runtime.Serialization.Formatters.Soap.SoapF ormatter. The
BinaryFormatter and SoapFormatter, as the names suggest, marshal types
in binary and SOAP format respectively. For metadata, .NET Remoting
relies on the common language runtime assemblies, which contain all the
relevant information about the data types they implement, and expose it
via reflection. The reliance on the assemblies for metadata makes it
easy to preserve the full runtime type-system fidelity. As a result,
when the .NET Remoting plumbing marshals data, it includes all of a
class's public and private members; handles object graphs correctly;
and supports all container types (e.g., System.Collections.Hashtable).
However, the reliance on runtime metadata also limits the reach of a
..NET Remoting system-a client has to understand .NET constructs in
order to communicate with a .NET Remoting endpoint. In addition to
pluggable formatters, the .NET Remoting layer supports pluggable
channels, which abstract away the details of how messages are sent.
There are two standard channels, one for raw TCP and one for HTTP.
Messages can be sent over either channel independent of format.
Distributed Application Design: ASP.NET Web Services vs. .NET Remoting
ASP.NET Web services favor the XML Schema type system, and provide a
simple programming model with broad cross-platform reach. .NET Remoting
favors the runtime type system, and provides a more complex programming
model with much more limited reach. This essential difference is the
primary factor in determining which technology to use. However, there
are a wide range of other design factors, including transport
protocols, host processes, security, performance, state management, and
support for transactions to consider as well.
Security
Since ASP.NET Web services rely on HTTP, they integrate with the
standard Internet security infrastructure. ASP.NET leverages the
security features available with IIS to provide strong support for
standard HTTP authentication schemes including Basic, Digest, digital
certificates, and even Microsoft® .NET Passport. (You can also use
Windows Integrated authentication, but only for clients in a trusted
domain.) One advantage of using the available HTTP authentication
schemes is that no code change is required in a Web service; IIS
performs authentication before the ASP.NET Web services are called.
ASP.NET also provides support for .NET Passport-based authentication
and other custom authentication schemes. ASP.NET supports access
control based on target URLs, and by integrating with the .NET code
access security (CAS) infrastructure. SSL can be used to ensure private
communication over the wire.
Although these standard transport-level techniques to secure Web
services are quite effective, they only go so far. In complex scenarios
involving multiple Web services in different trust domains, you have to
build custom ad hoc solutions. Microsoft and others are working on a
set of security specifications that build on the extensibility of SOAP
messages to offer message-level security capabilities. One of these is
the XML Web Services Security Language (WS-Security), which defines a
framework for message-level credential transfer, message integrity, and
message confidentiality.
As noted in the previous section, the .NET Remoting plumbing does not
secure cross-process invocations in the general case. A .NET Remoting
endpoint hosted in IIS with ASP.NET can leverage all the same security
features available to ASP.NET Web services, including support for
secure communication over the wire using SSL. If you are using the TCP
channel or the HTTP channel hosted in processes other than
aspnet_wp.exe, you have to implement authentication, authorization and
privacy mechanisms yourself.
One additional security concern is the ability to execute code from a
semi-trusted environment without having to change the default security
policy. ASP.NET Web Services client proxies work in these environments,
but .NET Remoting proxies do not. In order to use a .NET Remoting proxy
from a semi-trusted environment, you need a special serialization
permission that is not given to code loaded from your intranet or the
Internet by default. If you want to use a .NET Remoting client from
within a semi-trusted environment, you have to alter the default
security policy for code loaded from those zones. In situations where
you are connecting to systems from clients running in a sandbox-like
a downloaded Windows Forms application, for instance-ASP.NET Web
Services are a simpler choice because security policy changes are not
required.
Conceptually, what is the difference between early-binding and
late-binding?
Early binding - Binding at Compile Time
Late Binding - Binding at Run Time
Early binding implies that the class of the called object is known at
compile-time; late-binding implies that the class is not known until
run-time, such as a call through an interface or via Reflection.
Early binding is the preferred method. It is the best performer because
your application binds directly to the address of the function being
called and there is no extra overhead in doing a run-time lookup. In
terms of overall execution speed, it is at least twice as fast as late
binding.
Early binding also provides type safety. When you have a reference set
to the component's type library, Visual Basic provides IntelliSense
support to help you code each function correctly. Visual Basic also
warns you if the data type of a parameter or return value is incorrect,
saving a lot of time when writing and debugging code.
Late binding is still useful in situations where the exact interface of
an object is not known at design-time. If your application seeks to
talk with multiple unknown servers or needs to invoke functions by name
(using the Visual Basic 6.0 CallByName function for example) then you
need to use late binding. Late binding is also useful to work around
compatibility problems between multiple versions of a component that
has improperly modified or adapted its interface between versions.
· What is an Assembly Qualified Name? Is it a filename? How is it
different?
An assembly qualified name isn't the filename of the assembly; it's the
internal name of the assembly combined with the assembly version,
culture, and public key, thus making it unique.
e.g. (""System.Xml.XmlDocument, System.Xml, Version=1.0.3300.0,
Culture=neutral, PublicKeyToken=b77a5c561934e089"")
· How is a strongly-named assembly different from one that isn't
strongly-named?
Strong names are used to enable the stricter naming requirements
associated with shared assemblies. These strong names are created by a
..NET utility - sn.exe
Strong names have three goals:
· Name uniqueness. Shared assemblies must have names that are
globally unique.
· Prevent name spoofing. Developers don't want someone else releasing
a subsequent version of one of your assemblies and falsely claim it
came from you, either by accident or intentionally.
· Provide identity on reference. When resolving a reference to an
assembly, strong names are used to guarantee the assembly that is
loaded came from the expected publisher.
Strong names are implemented using standard public key cryptography. In
general, the process works as follows: The author of an assembly
generates a key pair (or uses an existing one), signs the file
containing the manifest with the private key, and makes the public key
available to callers. When references are made to the assembly, the
caller records the public key corresponding to the private key used to
generate the strong name.
Weak named assemblies are not suitable to be added in GAC and shared.
It is essential for an assembly to be strong named.
Strong naming prevents tampering and enables assemblies to be placed in
the GAC alongside other assemblies of the same name.
· How does the generational garbage collector in the .NET CLR manage
object lifetime? What is non-deterministic finalization?
The hugely simplistic version is that every time it garbage-collects,
it starts by assuming everything to be garbage, then goes through and
builds a list of everything reachable. Those become not-garbage,
everything else doesn't, and gets thrown away. What makes it
generational is that every time an object goes through this process and
survives, it is noted as being a member of an older generation (up to
2, right now). When the garbage-collector is trying to free memory, it
starts with the lowest generation (0) and only works up to higher ones
if it can't free up enough space, on the grounds that shorter-lived
objects are more likely to have been freed than longer-lived ones.
Non-deterministic finalization implies that the destructor (if any) of
an object will not necessarily be run (nor its memory cleaned up, but
that's a relatively minor issue) immediately upon its going out of
scope. Instead, it will wait until first the garbage collector gets
around to finding it, and then the finalisation queue empties down to
it; and if the process ends before this happens, it may not be
finalised at all. (Although the operating system will usually clean up
any process-external resources left open - note the usually there,
especially as the exceptions tend to hurt a lot.)
· What is the difference between Finalize() and Dispose()?
Dispose() is called by the user of an object to indicate that he is
finished with it, enabling that object to release any unmanaged
resources it holds. Finalize() is called by the run-time to allow an
object which has not had Dispose() called on it to do the same.
However, Dispose() operates determinalistically, whereas there is no
guarantee that Finalize() will be called immediately when an object
goes out of scope - or indeed at all, if the program ends before that
object is GCed - and as such Dispose() is generally preferred.

· How is the using() pattern useful? What is IDisposable? How does it
support deterministic finalization?
The using() pattern is useful because it ensures that Dispose() will
always be called when a disposable object (defined as one that
implements IDisposable, and thus the Dispose() method) goes out of
scope, even if it does so by an exception being thrown, and thus that
resources are always released.

· What does this useful command line do? tasklist /m "mscor*"
Lists all the applications and associated tasks/process currently
running on the system with a module whose name begins "mscor" loaded
into them; which in nearly all cases means "all the .NET processes".

· What's wrong with a line like this? DateTime.Parse(myString);
Therez nothing wrong with this declaration.Converts the specified
string representation of a date and time to its DateTime equivalent.But
If the string is not a valid DateTime,It throws an exception.

· What are PDBs? Where must they be located for debugging to work?
A program database (PDB) files holds debugging and project state
information that allows incremental linking of debug configuration of
your program.There are several different types of symbolic debugging
information. The default type for Microsoft compiler is the so-called
PDB file. The compiler setting for creating this file is /Zi, or /ZI
for C/C++(which creates a PDB file with additional information that
enables a feature called ""Edit and Continue"") or a Visual
Basic/C#/JScript .NET program with /debug.
A PDB file is a separate file, placed by default in the Debug project
subdirectory, that has the same name as the executable file with the
extension .pdb. Note that the Visual C++ compiler by default creates an
additional PDB file called VC60.pdb for VisulaC++6.0 and VC70.PDB file
for VisulaC++7.0. The compiler creates this file during compilation of
the source code, when the compiler isn't aware of the final name of the
executable. The linker can merge this temporary PDB file into the main
one if you tell it to, but it won't do it by default. The PDB file can
be useful to display the detailed stack trace with source files and
line numbers.
· What is FullTrust? Do GAC'ed assemblies have FullTrust?
Before the .NET Framework existed, Windows had two levels of trust for
downloaded code. This old model was a binary trust model. You only had
two choices: Full Trust, and No Trust. The code could either do
anything you could do, or it wouldn't run at all.

The permission sets in .NET include FullTrust, SkipVerification,
Execution, Nothing, LocalIntranet, Internet and Everything. Full Trust
Grants unrestricted permissions to system resources. Fully trusted code
run by a normal, nonprivileged user cannot do administrative tasks, but
can access any resources the user can access, and do anything the user
can do. From a security standpoint, you can think of fully trusted code
as being similar to native, unmanaged code, like a traditional ActiveX
control.
GAC assemblies are granted FullTrust. In v1.0 and 1.1, the fact that
assemblies in the GAC seem to always get a FullTrust grant is actually
a side effect of the fact that the GAC lives on the local machine. If
anyone were to lock down the security policy by changing the grant set
of the local machine to something less than FullTrust, and if your
assembly did not get extra permission from some other code group, it
would no longer have FullTrust even though it lives in the GAC.

· What does this do? gacutil /l | find /i "Corillian"
The Global Assembly Cache tool allows you to view and manipulate the
contents of the global assembly cache and download cache.The tool comes
with various optional params to do that.
""/l"" option Lists the contents of the global assembly cache. If you
specify the assemblyName parameter(/l [assemblyName]), the tool lists
only the assemblies matching that name.

· What does this do .. sn -t foo.dll ?
Sn -t option displays the token for the public key stored in infile.
The contents of infile must be previously generated using -p.
Sn.exe computes the token using a hash function from the public key. To
save space, the common language runtime stores public key tokens in the
manifest as part of a reference to another assembly when it records a
dependency to an assembly that has a strong name. The -tp option
displays the public key in addition to the token.

· How do you generate a strong name?
..NET provides an utility called strong name tool. You can run this
toolfrom the VS.NET command prompt to generate a strong name with an
option "-k" and providing the strong key file name. i.e. sn- -k <
file-name >

· What is the difference between a Debug and Release build? Is there
a significant speed difference? Why or why not?
The Debug build is the program compiled with full symbolic debug
information and no optimization. The Release build is the program
compiled employing optimization and contains no symbolic debug
information. These settings can be changed as per need from Project
Configuration properties. The release runs faster since it does not
have any debug symbols and is optimized.
· Explain the use of virtual, sealed, override, and abstract.
Abstract: The keyword can be applied for a class or method.
1. Class: If we use abstract keyword for a class it makes the
class an abstract class, which means it cant be instantiated. Though
it is not nessacary to make all the method within the abstract class
to be virtual. ie, Abstract class can have concrete methods
2. Method: If we make a method as abstract, we dont need to provide
implementation
of the method in the class but the derived class need to
implement/override this method.

Sealed: It can be applied on a class and methods. It stops the type
from further derivation i.e no one can derive class
from a sealed class,ie A sealed class cannot be inherited.A sealed
class cannot be a abstract class.A compile time error is thrown if you
try to specify sealed class as a base class.
When an instance method declaration includes a sealed modifier, that
method is said to be a sealed method. If an instance method declaration
includes the sealed modifier, it must also include the override
modifier. Use of the sealed modifier prevents a derived class from
further overriding the method For Egs: sealed override public void
Sample() { Console.WriteLine("Sealed Method"); }
Virtual & Override: Virtual & Override keywords provides runtime
polymorphism. A base class can make some of its methods as virtual
which allows the derived class a chance to override the base class
implementation by using override keyword.

For e.g. class Shape
{
int a
public virtual void Display()
{
Console.WriteLine("Shape");
}
}

class Rectangle:Shape
{
public override void Display()
{
Console.WriteLine("Derived");
}
}
· Explain the importance and use of each, Version, Culture and
PublicKeyToken for an assembly.
This three alongwith name of the assembly provide a strong name or
fully qualified name to the assembly. When a assebly is referenced with
all three.
PublicKeyToken: Each assembly can have a public key embedded in its
manifest that identifies the developer. This ensures that once the
assembly ships, no one can modify the code or other resources contained
in the assembly.

Culture: Specifies which culture the assembly supports

Version: The version number of the assembly.It is of the following form
major.minor.build.revision.
· Explain the differences between public, protected, private and
internal. ?
These all are access modifier and they governs the access level. They
can be applied to class, methods, fields.

Public: Allows class, methods, fields to be accessible from anywhere
i.e. within and outside an assembly.
Private: When applied to field and method allows to be accessible
within a class.
Protected: Similar to private but can be accessed by members of derived
class also.
Internal: They are public within the assembly i.e. they can be accessed
by anyone within an assembly but outside assembly they are not visible.
· What is the difference between typeof(foo) and myFoo.GetType()?
Typeof is operator which applied to a object returns System.Type
object. Typeof cannot be overloaded white GetType has lot of
overloads.GetType is a method which also returns System.Type of an
object. GetType is used to get the runtime type of the object.
Example from MSDN showing Gettype used to retrive type at untime:-
public class MyBaseClass: Object {
}
public class MyDerivedClass: MyBaseClass {
}
public class Test {
public static void Main() {
MyBaseClass myBase = new MyBaseClass();
MyDerivedClass myDerived = new MyDerivedClass();
object o = myDerived;
MyBaseClass b = myDerived;
Console.WriteLine("mybase: Type is {0}", myBase.GetType());
Console.WriteLine("myDerived: Type is {0}", myDerived.GetType());
Console.WriteLine("object o = myDerived: Type is {0}",
o.GetType());
Console.WriteLine("MyBaseClass b = myDerived: Type is {0}",
b.GetType());
}
}

/*
This code produces the following output.
mybase: Type is MyBaseClass
myDerived: Type is MyDerivedClass
object o = myDerived: Type is MyDerivedClass
MyBaseClass b = myDerived: Type is MyDerivedClass
*/
· Can "this" be used within a static method?
No 'This' cannot be used in a static method. As only static
variables/methods can be used in a static method.

· What is the purpose of XML Namespaces?
An XML Namespace is a collection of element types and attribute names.
It consists of 2 parts
1) The first part is the URI used to identify the namespace
2) The second part is the element type or attribute name itself.
Together they form a unique name. The various purpose of XML Namespace
are
1. Combine fragments from different documents without any naming
conflicts. (See example below.)
2. Write reusable code modules that can be invoked for specific
elements and attributes. Universally unique names guarantee that
such modules are invoked only for the correct elements and attributes.
3. Define elements and attributes that can be reused in other schemas
or instance documents without fear of name collisions. For
example, you might use XHTML elements in a parts catalog to provide
part descriptions. Or you might use the nil attribute
defined in XML Schemas to indicate a missing value.
< Department >
< Name >DVS1< /Name >
< addr:Address
xmlns:addr="http://www.tu-darmstadt.de/ito/addresses" >
< addr:Street >Wilhelminenstr. 7< /addr:Street >
< addr:City >Darmstadt< /addr:City >
< addr:State >Hessen< /addr:State >
< addr:Country >Germany< /addr:Country >
< addr:PostalCode >D-64285< /addr:PostalCode >
< /addr:Address >
< serv:Server xmlns:serv="http://www.tu-darmstadt.de/ito/servers"
>
< serv:Name >OurWebServer< /serv:Name >
< serv:Address >123.45.67.8< /serv:Address >
< /serv:Server >
< /Department >
· What is difference between MetaData and Manifest ?
Metadata and Manifest forms an integral part of an assembly( dll / exe
) in .net framework .
Out of which Metadata is a mandatory component , which as the name
suggests gives the details about various components of IL code viz :
Methods , properties , fields , class etc.
Essentially Metadata maintains details in form of tables like Methods
Metadata tables , Properties Metadata tables , which maintains the list
of given type and other details like access specifier , return type
etc.
Now Manifest is a part of metadata only , fully called as "manifest
metadata tables" , it contains the details of the references needed
by the assembly of any other external assembly / type , it could be a
custom assembly or standard System namespace .
Now for an assembly that can independently exists and used in the .Net
world both the things ( Metadata with Manifest ) are mandatory , so
that it can be fully described assembly and can be ported anywhere
without any system dependency . Essentially .Net framework can read all
assembly related information from assembly itself at runtime .
But for .Net modules , that can't be used independently , until they
are being packaged as a part of an assembly , they don't contain
Manifest but their complete structure is defined by their respective
metadata .
Ultimately .Net modules use Manifest Metadata tables of parent assembly
which contain them.
· What is the use of Internal keyword?
Internal keyword is one of the access specifier available in .Net
framework , that makes a type visible in a given assembly , for e.g :
a single dll can contain multiple modules , essentially a multi file
assembly , but it forms a single binary component , so any type with
internal keyword will be visible throughout the assembly and can be
used in any of the modules .

· What actually happes when you add a something to
arraylistcollection ?
Following things will happen :
Arraylist is a dynamic array class in c# in System.Collections
namespace derived from interfaces - ICollection , IList , ICloneable
, IConvertible . It terms of in memory structure following is the
implementation .
a. Check up the total space if there's any free space on the declared
list .
b. If yes add the new item and increase count by 1 .
c. If No Copy the whole thing to a temporary Array of Last Max. Size .
d. Create new Array with size ( Last Array Size + Increase Value )
e. Copy back values from temp and reference this new array as original
array .
f. Must doing Method updates too , need to check it up .
· What is Boxing and unboxing? Does it occure automaatically or u
need to write code to box and unbox?
Boxing - Process of converting a System.ValueType to Reference Type ,
Mostly base class System.Object type and allocating it memory on Heap
..Reverse is unboxing , but can only be done with prior boxed variables.
Boxing is always implicit but Unboxing needs to be explicitly done via
casting , thus ensuring the value type contained inside .
· How Boxing and unboxing occures in memory?
Boxing converts value type to reference type , thus allocating memory
on Heap . Unboxing converts already boxed reference types to value
types through explicit casting , thus allocating memory on stack .

· Why only boxed types can be unboxed?
Unboxing is the process of converting a Reference type variable to
Value type and thus allocating memory on the stack . It happens only to
those Reference type variables that have been earlier created by Boxing
of a Value Type , therefore internally they contain a value type ,
which can be obtained through explicit casting . For any other
Reference type , they don't internally contain a Value type to
Unboxed via explicit casting . This is why only boxed types can be
unboxed.

Jan 17 '07 #1
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