C# strings

[Trevor]

I have a couple of questions regarding C# strings.

1) Sometimes I see a string in someone else's code like:

string foo = @"bar";

What does the '@' do for you?
2) Is there a performance loss if I start concatenating strings together
with the + operator ? In Java, they discouraged code like this:

string command = "CMD " + var1 + " " + var2;

The reason is because of all of the temporary String objects that get
created in the meantime. The solution is to use a StringBuffer like so:

StringBuffer command = new StringBuffer("C MD ");
command.append( var1);
command.append( ' ');
command.append( var2);
System.out.prin tln(command.toS tring());

This is less expensive than the above code because String objects are not
being created left & right. Does C# have the same problem? I noticed that
C# has a StringBuilder class which is just like the Java StringBuffer class.
Should I use StringBuffer in cases like the above where I need to
concatenate multiple strings to one string?

[Joe Mayo]

Hi Trevor,

Please see response in-line.

Joe
--
http://www.csharp-station.com

"Trevor" <tr****@nospam. com> wrote in message
news:uC******** ******@TK2MSFTN GP12.phx.gbl...

1) Sometimes I see a string in someone else's code like:

string foo = @"bar";

What does the '@' do for you?
That's a verbatim string literal, which preserves characters between the
double quotes. One of its uses is when you want to make file paths more
readable. For example, in a normal string, you would escape the path
separator like this:

"c:\\MyDir\\MyS ubDir\\MyFile.c s"

Instead, you can do this:

@"c:\MyDir\MySu bDir\MyFile.cs"

Also, you can sometimes do something like this:

@"
This is some text that I
want to show on the
console with line feeds
"
Instead of:

"This is some text that I\n want to show on the\n console with line feeds"

or something else less readable.
2) Is there a performance loss if I start concatenating strings together
with the + operator ? In Java, they discouraged code like this:

string command = "CMD " + var1 + " " + var2;

Yes, there is a performance penalty with these concatenations because of new
string objects being created on each concatenation. The string type is
immutable.
Should I use StringBuffer in cases like the above where I need to
concatenate multiple strings to one string?

You should use the StringBuilder. I use a rule-of-thumb that when I have 4
or more concatenations, I will use a StringBuilder instead.

[Eric Eggermann]

"Trevor" <tr****@nospam. com> wrote in message
news:uC******** ******@TK2MSFTN GP12.phx.gbl...

I have a couple of questions regarding C# strings.

1) Sometimes I see a string in someone else's code like:

string foo = @"bar";

What does the '@' do for you?
2) Is there a performance loss if I start concatenating strings together
with the + operator ? In Java, they discouraged code like this:

string command = "CMD " + var1 + " " + var2;

Hello Trevor,

#2: C# is much the same, and the string builder class is provided for that.
I think though that if you are just concatenating a couple of variables, the
performance hit isn't so hard. It's building large strings where string
builder is handy. There's been lots of discussion on this topic, but for
myself, I use string builder if I'm concatenating more than say 10 items.

#1: The @ sign causes the compiler to treat the string as it is, and not
look for escape characters and whatnot, or something like that. I only know
that if I want to hardcode a folder and filename, or something like that, I
have to use the @"[string]" or it doesn't work properly. Surely someone else
will give a more definitive answer. Looking forward to that myself.

Eric

[Nicholas Paldino [.NET/C# MVP]]

Trevor,

See inline.

"Trevor" <tr****@nospam. com> wrote in message
news:uC******** ******@TK2MSFTN GP12.phx.gbl...

I have a couple of questions regarding C# strings.

1) Sometimes I see a string in someone else's code like:

string foo = @"bar";

What does the '@' do for you?
The amperstand means to take the string as a literal, and not interpret
escape codes. For example, when working with paths, you have to use "\"
twice for each path separator, because "\" needs to be escaped, like so:

"c:\\temp"

However, with a string literal, there are no escape characters, so you
don't have to worry. You can write this:

@"c:\temp"


2) Is there a performance loss if I start concatenating strings together
with the + operator ? In Java, they discouraged code like this:

string command = "CMD " + var1 + " " + var2;

The reason is because of all of the temporary String objects that get
created in the meantime. The solution is to use a StringBuffer like so:

StringBuffer command = new StringBuffer("C MD ");
command.append( var1);
command.append( ' ');
command.append( var2);
System.out.prin tln(command.toS tring());

This is less expensive than the above code because String objects are not
being created left & right. Does C# have the same problem? I noticed that C# has a StringBuilder class which is just like the Java StringBuffer class. Should I use StringBuffer in cases like the above where I need to
concatenate multiple strings to one string?
Generally speaking, if you have a lot of string manipulation to do, then
you should use a StringBuilder instance to do it. It will be faster than
just concatenating strings. It should be noted that the following line:

string command = "CMD " + var1 + " " + var2;

Is actually going to be compiled into:

string command = String.Concat(" CMD ", var1, " ", var2);

Underneath the covers, Concat uses a StringBuilder instance to do its
work. Also, it should be noted that the compiler treats the concatenation
of two string literals as a single instance. In other words:

"Hello " + "there"

Is compiled into:

"Hello there"

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard. caspershouse.co m

[Lawrence Oluyede]

"Trevor" <tr****@nospam. com> writes:

1) Sometimes I see a string in someone else's code like:

string foo = @"bar";

What does the '@' do for you?
In that case it does nothing, the @ symbol stands for
"treat the string as a raw string and don't escape nothing"

So if you are (for example) using a string to store a path
you can do that in the two following ways:

string path = "c:\\windows\\s ystem32"

or

string path = @"c:\windows\sy stem32"

You gain the same behavior with other escape chars (\n, \t and so on)
2) Is there a performance loss if I start concatenating strings together
with the + operator ? In Java, they discouraged code like this:

string command = "CMD " + var1 + " " + var2;

The reason is because of all of the temporary String objects that get
created in the meantime. The solution is to use a StringBuffer like so:

StringBuffer command = new StringBuffer("C MD ");
command.append( var1);
command.append( ' ');
command.append( var2);
System.out.prin tln(command.toS tring());

Yeah, in .NET is pretty the same thing. It's discouraged to concatenate
strings cause they are "immutable" (a Python definition) and every
"string1" + "string2" generates a new instance (AFAIK). So .NET put in
place a class called StringBuilder (used in the same way as the
StringBufffer above) in the System.Text namespace

example:

using System.Text;

..... blah blah...

StringBuilder command = new StringBuilder(" CMD ");
command.Append( var1);
command.Append( " ");
command.Append( var2);
Console.WriteLi ne(command.ToSt ring());
--
Lawrence "Rhymes" Oluyede
http://loluyede.blogspot.com

[Cowboy \(Gregory A. Beamer\)]

@ says "This is my string, including any special characters". In other
cases, you have to include special characters. For example, to have the
string "10\10" you would write either as "10\\10" or @"10\10".

--
Gregory A. Beamer
MVP; MCP: +I, SE, SD, DBA

*************** *************** *************** *************** **********
Think Outside the Box!
*************** *************** *************** *************** **********
"Trevor" <tr****@nospam. com> wrote in message
news:uC******** ******@TK2MSFTN GP12.phx.gbl...

I have a couple of questions regarding C# strings.

1) Sometimes I see a string in someone else's code like:

string foo = @"bar";

What does the '@' do for you?
2) Is there a performance loss if I start concatenating strings together
with the + operator ? In Java, they discouraged code like this:

string command = "CMD " + var1 + " " + var2;

The reason is because of all of the temporary String objects that get
created in the meantime. The solution is to use a StringBuffer like so:

StringBuffer command = new StringBuffer("C MD ");
command.append( var1);
command.append( ' ');
command.append( var2);
System.out.prin tln(command.toS tring());

This is less expensive than the above code because String objects are not
being created left & right. Does C# have the same problem? I noticed that C# has a StringBuilder class which is just like the Java StringBuffer class. Should I use StringBuffer in cases like the above where I need to
concatenate multiple strings to one string?

[Cowboy \(Gregory A. Beamer\)]

StringBuilder is more efficient when firing off a lot of manipulation.

Inefficient
----------
string x = "something" ;
x += "Something else";
x += "Something else";
x += "Something else";
x += "Something else";
x += "Something else";

It would be better to use StringBuilder here.

string x = "something" + var1 + "something else" + var2;

Not a big issue here, as the end string is not being manipulated over and
over again (creating a new string each time). If you are simply concating,
adding to a string is fine. The benefit of the StringBuilder is cleaner
code, but more typing, especially when concating 100s of variables.
--
Gregory A. Beamer
MVP; MCP: +I, SE, SD, DBA

*************** *************** *************** *************** **********
Think Outside the Box!
*************** *************** *************** *************** **********
"Trevor" <tr****@nospam. com> wrote in message
news:uC******** ******@TK2MSFTN GP12.phx.gbl...

I have a couple of questions regarding C# strings.

1) Sometimes I see a string in someone else's code like:

string foo = @"bar";

What does the '@' do for you?
2) Is there a performance loss if I start concatenating strings together
with the + operator ? In Java, they discouraged code like this:

string command = "CMD " + var1 + " " + var2;

The reason is because of all of the temporary String objects that get
created in the meantime. The solution is to use a StringBuffer like so:

StringBuffer command = new StringBuffer("C MD ");
command.append( var1);
command.append( ' ');
command.append( var2);
System.out.prin tln(command.toS tring());

This is less expensive than the above code because String objects are not
being created left & right. Does C# have the same problem? I noticed that C# has a StringBuilder class which is just like the Java StringBuffer class. Should I use StringBuffer in cases like the above where I need to
concatenate multiple strings to one string?

[Madhu [MVP]]

Hi,

Answers inline...

Regards,
Madhu

MVP | MCSD.NET

-----Original Message-----
I have a couple of questions regarding C# strings.

1) Sometimes I see a string in someone else's code like:

string foo = @"bar";

What does the '@' do for you?
All the escape sequence are not processed if you have
the '@' character. thus making things very simple.
for example: if you want the string to have the value
c:\docs\sample. txt, you can write it in two ways,
string foo = "c:\\docs\\samp le.txt";
or
string foo = @"c:\docs\sampl e.txt";
2) Is there a performance loss if I start concatenating strings togetherwith the + operator ? In Java, they discouraged code like this:
string command = "CMD " + var1 + " " + var2;

The reason is because of all of the temporary String objects that getcreated in the meantime. The solution is to use a StringBuffer like so:
StringBuffer command = new StringBuffer("C MD ");
command.append (var1);
command.append (' ');
command.append (var2);
System.out.pri ntln(command.to String());

This is less expensive than the above code because String objects are notbeing created left & right. Does C# have the same problem? I noticed thatC# has a StringBuilder class which is just like the Java StringBuffer class.Should I use StringBuffer in cases like the above where I need toconcatenate multiple strings to one string?

You are right!!! because in both the cases String is
immutable and thus creates lot of string objects.

[Jon Skeet [C# MVP]]

Trevor <tr****@nospam. com> wrote:

I have a couple of questions regarding C# strings.

1) Sometimes I see a string in someone else's code like:

string foo = @"bar";

What does the '@' do for you?
It makes it a "verbatim string literal" which means you don't have to
escape backslashes and the like.
2) Is there a performance loss if I start concatenating strings together
with the + operator ? In Java, they discouraged code like this:

string command = "CMD " + var1 + " " + var2;

The reason is because of all of the temporary String objects that get
created in the meantime. The solution is to use a StringBuffer like so:

StringBuffer command = new StringBuffer("C MD ");
command.append( var1);
command.append( ' ');
command.append( var2);
System.out.prin tln(command.toS tring());

This is less expensive than the above code because String objects are not
being created left & right.

It's really *not* any less expensive. Please read
http://www.pobox.com/~skeet/java/stringbuffer.html for more
information.

..NET's StringBuilder is indeed very similar to Java's StringBuffer, and
is useful in exactly the same circumstances - which doesn't include the
above.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Joe Mayo <jm***@nospamAt CSharpDashStati on.com> wrote:

Please see response in-line.
[Please fix your posting style so your response doesn't end up below
your sig separator, otherwise clients which automatically strip sigs
end up having problems quoting your post.]

string command = "CMD " + var1 + " " + var2;

Yes, there is a performance penalty with these concatenations because
of new string objects being created on each concatenation. The string
type is immutable.

No, there's no performance penalty above. Only a single string is being
created, as the above gets turned into

string command = String.Concat ("CMD ", var1, " ", var2);

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too