I'm confused about the proper use and usefulness of namespaces. I beleive I
understand the purpose is so the developer can put classes within namespaces
to essentially organize your code. And I understand that you declare your
intention to use a namespace within a page through the "Inherits" attribute.
I know that using "Inherits" isn't absolutely necessary, it's just
recommended so the developer doesn't have to type out the entire namespace
in code. I know that namespaces have to appear in the project assembly,
however...
How does the assembly find a namespace that the developer has written????
In all the examples I've seen, namespaces have been written in codebehind
pages. How does this make them accessible to the entire project? What's to
prevent a duplicate namespace from being written in a different codebehind
page? Is there a better place to write all the project namespaces for more
centralized accessibility?
And finally, how do namespaces DIFFER from classes?
Random
Nov 18 '05
11 1040
hoo, boy. What a thread this is turning out to be. First, I do understand,
and you have confirmed a lot of things I have suspected.
Let me take a different approach on this, if I may. Let's say I have two
aspx pages that I know I want utilize a specific function within, that is
contained in a class. Without having to copy/paste this function into a
different class in a different codebehind page (because I don't want them to
have the same codebehind page), how can I reference this function.
NONE of the tutorials or materials I have read go beyond a one page example.
Seperation of code and HTML... fine. It's the sharing of code through
namespaces and classes that I'm having difficulty grasping at this point.
"Kevin Spencer" <uc*@ftc.gov> wrote in message
news:%2******** *******@tk2msft ngp13.phx.gbl.. . Hi Random,
I realize that while Visual Studio automatically encourages a 1 to 1 relationship between aspx and codebehind pages, this does not
necessarily need to be the case. I also realize that errors would occur during compiling if the same class was written in different places. What I
don't understand is how Visual Studio keeps track in the assembly of where all these written classes are? A .Net assembly is a compiled DLL. The data in the code files is compiled into binary code in the DLL, including all the namespace information, references, etc. Once compiled into a DLL, your CodeBehind class files are nothing but dead weight. They are not used; the DLL is. So, forget about
the "written classes". Think about the classes themselves, rather than the
code you write to create them.
As another example, what if I wrote an aspx page that inherited a class contained in a codebehind page that was NOT referenced by the aspx page? You wouldn't be able to compile OR use it. An aspx Page is a composite of
2 distinct entities: the Page Template (.aspx) and the CodeBehind class. The Page Template inherits the CodeBehind class, which inherits System.Web.UI.P age. The .aspx file by itself can do nothing without CodeBehind, whether that is in the same (.aspx) file as the Page Template,
a CodeBehind file, or a DLL. The important thing is that the .aspx Page Template has a reference in it telling it where to look for the class definition that it inherits. If the CodeBehind is compiled into a DLL, and that DLL is in one of the locations that ASP.Net can find it (Global Assembly Cache or \bin folder), ASP.Net uses Reflection to query the assembly for the class, based upon the NameSpace and Class name of the class. All of this information is contained in the DLL itself.
Since the class is found in the assembly, how would the aspx page know where to look? When the code is all compiled, does it automatically all the classes available from a central source? And if this is the case, wouldn't it make more sense to put all the code into a *.vb or *.cs file where it can be centrally referenced?
Again, only the CodeBehind is compiled. The Page Template (.aspx) must
have a Reference in it telling it where to find the CodeBehind class. There IS not "central source" for information about .Net classes. That is why you
can simply put your DLLs into the \bin folder of your web app, and they will
be found. Once found, the .Net platform can query the DLLs to find the DLL needed, and the class inside the DLL to use.
Take a look at the following example, from an ASPX page I created:
<%@ Page Language="vb" AutoEventWireup ="false" Codebehind="Web Form1.aspx.vb" Inherits="Contr olTest.WebForm1 "%>
The "CodeBehind " attribute is there solely for the benefit of Visual Studio.Net. It tells VS.Net what file to compile to create the DLL used by the Page class(es). The "Inherits" directive is the key. Note that it contains no information about the location of the DLL. ASP.Net KNOWS where the DLL can be located. Instead, it contains a reference to a NameSpace
and a class, which it can find by using Reflection on the assemblies in the
\bin folder and the GAC.
-- HTH, Kevin Spencer .Net Developer Microsoft MVP Big things are made up of lots of little things.
"Random" <ci*******@hotm ail.com> wrote in message news:#D******** ******@TK2MSFTN GP10.phx.gbl... I know you are not trying to offend, Marina, but I am an experienced programmer, just new to .NET, and I have read a lot, from the basics. I am disappointed that a lot of the 'beginner' material has been unhelpful
when it comes to an architectural overview of ASP.NET, which is what I am trying to clarify here. I thought that by asking 'basic' questions, I might
get a better understanding of how things fit into the whole. So please be patient with me in this.
I realize that while Visual Studio automatically encourages a 1 to 1 relationship between aspx and codebehind pages, this does not
necessarily need to be the case. I also realize that errors would occur during compiling if the same class was written in different places. What I
don't understand is how Visual Studio keeps track in the assembly of where all these written classes are?
As another example, what if I wrote an aspx page that inherited a class contained in a codebehind page that was NOT referenced by the aspx page? Since the class is found in the assembly, how would the aspx page know where to look? When the code is all compiled, does it automatically all the classes available from a central source? And if this is the case, wouldn't it make more sense to put all the code into a *.vb or *.cs file where it can be centrally referenced?
You are right, I think there is something very simple I am misunderstandin g, but for the life of me, I can't locate the answer anwhere.
Random
"Marina" <so*****@nospam .com> wrote in message news:e7******** ********@TK2MSF TNGP12.phx.gbl. .. I have no idea what you are talking about to be honest.
The class is already in a namespace - the Inherits attribute is just referencing. It isn't creating a new namespace or a new class. So I have no idea what you are talking about when you ask about namespaces being written in central locations.
You can have any number of pages inherit from the same class - as long as that class actually exists. In the visual studio model, you would have to manually do that, because it assume a 1 to 1 ration between pages and code behind classes.
If you tried to compiled two classes with the same name into the same assembly, the compiler would not allow you to do this. The assembly itself knows what classes it has, and what namespace each one is in, in it's manifest.
I would recommend you start at the very basics of ASP.NET, it sounds like you are missing some basic concept about how this all works. In your first post you asked about the difference between a namespace and a class -
so it seems like you need to go to the beginning of .NET, and not just into the middle of ASP.NET.
"Random" <ci*******@hotm ail.com> wrote in message news:ua******** ******@TK2MSFTN GP09.phx.gbl... > Okay, that clarifies the "Inherits" vs. "Imports" question very
well. > Thanks. > > As far as the namespace being available in the assembly, though, let me give > you an example... > > Using the portal code I gave before, would I be able to write
another aspx > page, use the same "Inherits=<full y qualified class name>" phrasing, without > that class being written into the different codebehind page
referenced in > the new aspx page? > > If yes, why? Shouldn't namespaces be written in a more centrally referenced > file? > > If no, then how can the assembly keep track of all the declared namespaces? > And what would it do if two or more codebehind references had the
same > namespace and class written in them? > > Random > > "Marina" <so*****@nospam .com> wrote in message > news:eq******** ******@TK2MSFTN GP10.phx.gbl... > > This inherits attribute, refers to the name of the class this page > inherits > > from. The class's name is CDefault, but it is located in the > > ASPNET.StarterK it.Portal namespace, and so the namespace has to preceed > it. > > > > At runtime, asp.net looks for a class with the name in the
inherits > > attribute. > > > > This has nothing to do with projects, or namespaces being
available. It is > > just the fully qualified name of the class. > > > > "Random" <ci*******@hotm ail.com> wrote in message > > news:OI******** *****@TK2MSFTNG P09.phx.gbl... > > > Hmm. I'm trying to teach myself from examples and tutorials and books. > > > Specifically in this case, I'm trying to learn from the MS > > PortalStarterKi t. > > > Specifically, the default page in that example has as the first line in > > > default.aspx: > > > > > > <%@ Page CodeBehind="Def ault.aspx.vb" language="vb" > > AutoEventWireup ="false" > > > Inherits="ASPNE T.StarterKit.Po rtal.CDefault" %> > > > > > > The codebehind page has: > > > > > > Namespace ASPNET.StarterK it.Portal > > > Public Class CDefault > > > Inherits System.Web.UI.P age > > > Private Sub Page_Load(ByVal sender As System.Object,
ByVal e As > > > System.EventArg s) Handles MyBase.Load > > > <code here> > > > End Sub > > > End Class > > > End Namespace > > > > > > I'm trying to find out how and why this works the way that it does. > It's > > > more complex than the examples given by tutorials and books. > > > > > > And again, I'm trying to figure out how the namespace declared here > makes > > > it's way into the assembly. And because it does, somehow, does that > make > > it > > > available through the entire project? > > > > > > Random > > > > > > "Marina" <so*****@nospam .com> wrote in message > > > news:%2******** ********@TK2MSF TNGP09.phx.gbl. .. > > > > First of all, namespaces can be used with the 'Imports'
keyword, so as > > not > > > > have to write out the full namespace for every class, not the > 'Inherits' > > > > attribute. > > > > > > > > Think of namespaces as folders in your file system, and
classes as the > > > files > > > > in them. So a namespace itself isn't anything but an organizational > > > > container for classes - just as a folder is just a container
for > files. > > > > Classes are the actual things that you instantiate, and call
methods > on. > > > > > > > > I didn't really understand your questions. I think they all
stem from > > not > > > > understanding what a namespace actually is. > > > > > > > > "Random" <ci*******@hotm ail.com> wrote in message > > > > news:uD******** ******@TK2MSFTN GP10.phx.gbl... > > > > > I'm confused about the proper use and usefulness of namespaces. I > > > beleive > > > > I > > > > > understand the purpose is so the developer can put classes within > > > > namespaces > > > > > to essentially organize your code. And I understand that
you > declare > > > your > > > > > intention to use a namespace within a page through the "Inherits" > > > > attribute. > > > > > I know that using "Inherits" isn't absolutely necessary,
it's just > > > > > recommended so the developer doesn't have to type out the entire > > > namespace > > > > > in code. I know that namespaces have to appear in the
project > > assembly, > > > > > however... > > > > > > > > > > How does the assembly find a namespace that the developer
has > > > written???? > > > > > In all the examples I've seen, namespaces have been written
in > > > codebehind > > > > > pages. How does this make them accessible to the entire project? > > > What's > > > > to > > > > > prevent a duplicate namespace from being written in a different > > > codebehind > > > > > page? Is there a better place to write all the project
namespaces > for > > > > more > > > > > centralized accessibility? > > > > > > > > > > And finally, how do namespaces DIFFER from classes? > > > > > > > > > > Random > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
You simply create a Class Library with the function(s) you want in it.
Reference the Class Library in your Page, and use it.
--
HTH,
Kevin Spencer
..Net Developer
Microsoft MVP
Big things are made up
of lots of little things.
"Random" <ci*******@hotm ail.com> wrote in message
news:#k******** ******@TK2MSFTN GP12.phx.gbl... hoo, boy. What a thread this is turning out to be. First, I do
understand, and you have confirmed a lot of things I have suspected.
Let me take a different approach on this, if I may. Let's say I have two aspx pages that I know I want utilize a specific function within, that is contained in a class. Without having to copy/paste this function into a different class in a different codebehind page (because I don't want them
to have the same codebehind page), how can I reference this function.
NONE of the tutorials or materials I have read go beyond a one page
example. Seperation of code and HTML... fine. It's the sharing of code through namespaces and classes that I'm having difficulty grasping at this point. "Kevin Spencer" <uc*@ftc.gov> wrote in message news:%2******** *******@tk2msft ngp13.phx.gbl.. . Hi Random,
I realize that while Visual Studio automatically encourages a 1 to 1 relationship between aspx and codebehind pages, this does not necessarily need to be the case. I also realize that errors would occur during compiling if the same class was written in different places. What I don't understand is how Visual Studio keeps track in the assembly of where
all these written classes are? A .Net assembly is a compiled DLL. The data in the code files is
compiled into binary code in the DLL, including all the namespace information, references, etc. Once compiled into a DLL, your CodeBehind class files
are nothing but dead weight. They are not used; the DLL is. So, forget about the "written classes". Think about the classes themselves, rather than the code you write to create them.
As another example, what if I wrote an aspx page that inherited a
class contained in a codebehind page that was NOT referenced by the aspx
page? You wouldn't be able to compile OR use it. An aspx Page is a composite
of 2 distinct entities: the Page Template (.aspx) and the CodeBehind class.
The Page Template inherits the CodeBehind class, which inherits System.Web.UI.P age. The .aspx file by itself can do nothing without CodeBehind, whether that is in the same (.aspx) file as the Page
Template, a CodeBehind file, or a DLL. The important thing is that the .aspx Page Template has a reference in it telling it where to look for the class definition that it inherits. If the CodeBehind is compiled into a DLL,
and that DLL is in one of the locations that ASP.Net can find it (Global Assembly Cache or \bin folder), ASP.Net uses Reflection to query the assembly for the class, based upon the NameSpace and Class name of the class. All of this information is contained in the DLL itself.
Since the class is found in the assembly, how would the aspx page know where to look? When the code is all compiled, does it automatically all the classes available from a central source? And if this is the case, wouldn't it make more sense to put all the code into a *.vb or *.cs file where
it can be centrally referenced?
Again, only the CodeBehind is compiled. The Page Template (.aspx) must
have a Reference in it telling it where to find the CodeBehind class. There
IS not "central source" for information about .Net classes. That is why you can simply put your DLLs into the \bin folder of your web app, and they will be found. Once found, the .Net platform can query the DLLs to find the DLL needed, and the class inside the DLL to use.
Take a look at the following example, from an ASPX page I created:
<%@ Page Language="vb" AutoEventWireup ="false" Codebehind="Web Form1.aspx.vb" Inherits="Contr olTest.WebForm1 "%>
The "CodeBehind " attribute is there solely for the benefit of Visual Studio.Net. It tells VS.Net what file to compile to create the DLL used
by the Page class(es). The "Inherits" directive is the key. Note that it contains no information about the location of the DLL. ASP.Net KNOWS
where the DLL can be located. Instead, it contains a reference to a NameSpace and a class, which it can find by using Reflection on the assemblies in the \bin folder and the GAC.
-- HTH, Kevin Spencer .Net Developer Microsoft MVP Big things are made up of lots of little things.
"Random" <ci*******@hotm ail.com> wrote in message news:#D******** ******@TK2MSFTN GP10.phx.gbl... I know you are not trying to offend, Marina, but I am an experienced programmer, just new to .NET, and I have read a lot, from the basics.
I am disappointed that a lot of the 'beginner' material has been unhelpful when it comes to an architectural overview of ASP.NET, which is what I am trying to clarify here. I thought that by asking 'basic' questions, I might get a better understanding of how things fit into the whole. So please be patient with me in this.
I realize that while Visual Studio automatically encourages a 1 to 1 relationship between aspx and codebehind pages, this does not necessarily need to be the case. I also realize that errors would occur during compiling if the same class was written in different places. What I don't understand is how Visual Studio keeps track in the assembly of where
all these written classes are?
As another example, what if I wrote an aspx page that inherited a
class contained in a codebehind page that was NOT referenced by the aspx
page? Since the class is found in the assembly, how would the aspx page know where to look? When the code is all compiled, does it automatically all the classes available from a central source? And if this is the case, wouldn't it make more sense to put all the code into a *.vb or *.cs file where
it can be centrally referenced?
You are right, I think there is something very simple I am misunderstandin g, but for the life of me, I can't locate the answer anwhere.
Random
"Marina" <so*****@nospam .com> wrote in message news:e7******** ********@TK2MSF TNGP12.phx.gbl. .. > I have no idea what you are talking about to be honest. > > The class is already in a namespace - the Inherits attribute is just > referencing. It isn't creating a new namespace or a new class. So I have no > idea what you are talking about when you ask about namespaces being written > in central locations. > > You can have any number of pages inherit from the same class - as
long as > that class actually exists. In the visual studio model, you would
have to > manually do that, because it assume a 1 to 1 ration between pages
and code > behind classes. > > If you tried to compiled two classes with the same name into the
same > assembly, the compiler would not allow you to do this. The assembly itself > knows what classes it has, and what namespace each one is in, in
it's > manifest. > > I would recommend you start at the very basics of ASP.NET, it sounds like > you are missing some basic concept about how this all works. In
your first > post you asked about the difference between a namespace and a
class - so it > seems like you need to go to the beginning of .NET, and not just
into the > middle of ASP.NET. > > "Random" <ci*******@hotm ail.com> wrote in message > news:ua******** ******@TK2MSFTN GP09.phx.gbl... > > Okay, that clarifies the "Inherits" vs. "Imports" question very well. > > Thanks. > > > > As far as the namespace being available in the assembly, though,
let me > give > > you an example... > > > > Using the portal code I gave before, would I be able to write another aspx > > page, use the same "Inherits=<full y qualified class name>"
phrasing, > without > > that class being written into the different codebehind page referenced in > > the new aspx page? > > > > If yes, why? Shouldn't namespaces be written in a more centrally > referenced > > file? > > > > If no, then how can the assembly keep track of all the declared > namespaces? > > And what would it do if two or more codebehind references had the same > > namespace and class written in them? > > > > Random > > > > "Marina" <so*****@nospam .com> wrote in message > > news:eq******** ******@TK2MSFTN GP10.phx.gbl... > > > This inherits attribute, refers to the name of the class this
page > > inherits > > > from. The class's name is CDefault, but it is located in the > > > ASPNET.StarterK it.Portal namespace, and so the namespace has to preceed > > it. > > > > > > At runtime, asp.net looks for a class with the name in the inherits > > > attribute. > > > > > > This has nothing to do with projects, or namespaces being available. It > is > > > just the fully qualified name of the class. > > > > > > "Random" <ci*******@hotm ail.com> wrote in message > > > news:OI******** *****@TK2MSFTNG P09.phx.gbl... > > > > Hmm. I'm trying to teach myself from examples and tutorials
and > books. > > > > Specifically in this case, I'm trying to learn from the MS > > > PortalStarterKi t. > > > > Specifically, the default page in that example has as the
first line > in > > > > default.aspx: > > > > > > > > <%@ Page CodeBehind="Def ault.aspx.vb" language="vb" > > > AutoEventWireup ="false" > > > > Inherits="ASPNE T.StarterKit.Po rtal.CDefault" %> > > > > > > > > The codebehind page has: > > > > > > > > Namespace ASPNET.StarterK it.Portal > > > > Public Class CDefault > > > > Inherits System.Web.UI.P age > > > > Private Sub Page_Load(ByVal sender As System.Object, ByVal e > As > > > > System.EventArg s) Handles MyBase.Load > > > > <code here> > > > > End Sub > > > > End Class > > > > End Namespace > > > > > > > > I'm trying to find out how and why this works the way that it does. > > It's > > > > more complex than the examples given by tutorials and books. > > > > > > > > And again, I'm trying to figure out how the namespace declared here > > makes > > > > it's way into the assembly. And because it does, somehow,
does that > > make > > > it > > > > available through the entire project? > > > > > > > > Random > > > > > > > > "Marina" <so*****@nospam .com> wrote in message > > > > news:%2******** ********@TK2MSF TNGP09.phx.gbl. .. > > > > > First of all, namespaces can be used with the 'Imports' keyword, so > as > > > not > > > > > have to write out the full namespace for every class, not
the > > 'Inherits' > > > > > attribute. > > > > > > > > > > Think of namespaces as folders in your file system, and classes as > the > > > > files > > > > > in them. So a namespace itself isn't anything but an organizational > > > > > container for classes - just as a folder is just a container for > > files. > > > > > Classes are the actual things that you instantiate, and call methods > > on. > > > > > > > > > > I didn't really understand your questions. I think they all stem > from > > > not > > > > > understanding what a namespace actually is. > > > > > > > > > > "Random" <ci*******@hotm ail.com> wrote in message > > > > > news:uD******** ******@TK2MSFTN GP10.phx.gbl... > > > > > > I'm confused about the proper use and usefulness of
namespaces. I > > > > beleive > > > > > I > > > > > > understand the purpose is so the developer can put classes within > > > > > namespaces > > > > > > to essentially organize your code. And I understand that you > > declare > > > > your > > > > > > intention to use a namespace within a page through the "Inherits" > > > > > attribute. > > > > > > I know that using "Inherits" isn't absolutely necessary, it's just > > > > > > recommended so the developer doesn't have to type out the entire > > > > namespace > > > > > > in code. I know that namespaces have to appear in the project > > > assembly, > > > > > > however... > > > > > > > > > > > > How does the assembly find a namespace that the developer has > > > > written???? > > > > > > In all the examples I've seen, namespaces have been
written in > > > > codebehind > > > > > > pages. How does this make them accessible to the entire project? > > > > What's > > > > > to > > > > > > prevent a duplicate namespace from being written in a different > > > > codebehind > > > > > > page? Is there a better place to write all the project namespaces > > for > > > > > more > > > > > > centralized accessibility? > > > > > > > > > > > > And finally, how do namespaces DIFFER from classes? > > > > > > > > > > > > Random > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
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