Vista - Using @ Sign at String Variables?

Hi,

one of my colleagues has written something like the following code in C#:

string a = @ConfigurationManager.AppSettings["MyTempPath"];

Is the @ sign of any use here?

Or is it just the compiler not giving an error because it's basically a string that's being attached to the @ sign?

Thanks for enlightening me!

Regards,
www.axeldahmen.de
Axel Dahmen

Axel,

The @ operator is of no use here. @ has two significant uses in C#:

1) Hard-coded string literals, which start with @ do not have their escape
sequences processed. For example, this allows you to avoid escaping file
paths (@"C:\folder\path.txt" vs "C:\\folder\\path.txt") but the disadvantage
is that you can't use any escape sequences such as \n (new line) or \r
(carriage return).

2) @ can be used for variable names shared with such C# keywords as 'new',
'class', etc. e.g.

string class = "test"; // Identifier expected, 'class' is keyword
string @class = "test"; // OK

HTH,
--
Stanimir Stoyanov
Microsoft MVP -- Visual C#

http://stoyanoff.info
"Axel Dahmen" <keentoknow@xxxxxx> wrote in message
news:%23SvbX5K1JHA.1644@xxxxxx
Hi,

one of my colleagues has written something like the following code in C#:

string a = @ConfigurationManager.AppSettings["MyTempPath"];

Is the @ sign of any use here?

Or is it just the compiler not giving an error because it's basically a
string that's being attached to the @ sign?

Thanks for enlightening me!

Regards,
www.axeldahmen.de
Axel Dahmen

Hi, Stanimir,

great, thanks. So there is no use for it with string variables, as I thought.

That variable name behaviour was new to me. Thanks for enlighten me on this one!

Best regards,
www.axeldahmen.de
Axel Dahemn



---------
"Stanimir Stoyanov (C# MVP)" <stoyanov@xxxxxx> schrieb im Newsbeitrag news:%23XT15YM1JHA.4288@xxxxxx

Hi Axel,

In addition to Stanimir's second point, here I quote the C# 3.0
specification 2.4.2 in case you and other community members who are
interested:

The prefix "@" enables the use of keywords as identifiers, which is useful
when interfacing with other programming languages. The character @ is not
actually part of the identifier, so the identifier might be seen in other
languages as a normal identifier, without the prefix. An identifier with an
@ prefix is called a verbatim identifier. Use of the @ prefix for
identifiers that are not keywords is permitted, but strongly discouraged as
a matter of style.

The example:
class @class
{
public static void @static(bool @bool) {
if (@bool)
System.Console.WriteLine("true");
else
System.Console.WriteLine("false");
}
}
class Class1
{
static void M() {
cl\u0061ss.st\u0061tic(true);
}
}
defines a class named "class" with a static method named "static" that
takes a parameter named "bool". Note that since Unicode escapes are not
permitted in keywords, the token "cl\u0061ss" is an identifier, and is the
same identifier as "@class".

Two identifiers are considered the same if they are identical after the
following transformations are applied, in order:
" The prefix "@", if used, is removed.
" Each unicode-escape-sequence is transformed into its corresponding
Unicode character.
" Any formatting-characters are removed.

The C# Language Specification Version 3.0 can be downloaded here:
http://download.microsoft.com/downlo...6-b2a8-75351c6
69b09/CSharp%20Language%20Specification.doc

Best regards,

Jie Wang (jiewan@xxxxxx, remove 'online.')

Microsoft Online Community Support

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