what does the @ do to strings and paths

[Peted]

I see many c# code samples that relate to strings or using strings in
file paths, that have an @ sign.

eg

string path1 = @"mydir";
string path2 = @"\mydir";
what does the @ do ?

Peted

[Jonathan Woods]

>From MSDN
----------------
@-quoted string literals start with @ and are enclosed in double
quotation marks.
For example:
@"good morning" // a string literal
The advantage of @-quoting is that escape sequences are not processed,
which makes it easy to write, for example, a fully qualified file
name:
@"c:\Docs\Source\a.txt" // rather than "c:\\Docs\\Source\\a.txt"
To include a double quotation mark in an @-quoted string, double it:
@"""Ahoy!"" cried the captain." // "Ahoy!" cried the captain.

[Ebbe Kristensen]

Peted wrote:

string path1 = @"mydir";
string path2 = @"\mydir";

what does the @ do ?

It disables the backslash as escape character. Without the @, the second
directory name should have been

string path2 = \\mydir;

Ebbe

[Jon Skeet [C# MVP]]

<Petedwrote:

I see many c# code samples that relate to strings or using strings in
file paths, that have an @ sign.

See http://pobox.com/~skeet/csharp/strings.html#literals

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

[=?Utf-8?B?QUEyZTcyRQ==?=]

I looked at the link; just wondered if you have views on code like this:

string myString = @"Line 1
Line 2
Line 3";

where \r\n is omitted but myString retains the linefeeds, as
MessageBox.Show(myString) confirms.

[Jon Skeet [C# MVP]]

AA2e72E <AA*****@discussions.microsoft.comwrote:

I looked at the link; just wondered if you have views on code like this:

string myString = @"Line 1
Line 2
Line 3";

where \r\n is omitted but myString retains the linefeeds, as
MessageBox.Show(myString) confirms.

Well, it can be very handy, but the main problem I have with it is
indentation - for the sake of reading it in the code, it's nice to have
the text indented appropriately, but often you want the initial text of
each line to be at the start of the line, without spaces or tabs.

Other than that, I don't have any major issues with it.

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

[Otis Mukinfus]

On Mon, 26 Feb 2007 01:39:07 -0800, AA2e72E <AA*****@discussions.microsoft.com>
wrote:

>I looked at the link; just wondered if you have views on code like this:

string myString = @"Line 1
Line 2
Line 3";

where \r\n is omitted but myString retains the linefeeds, as
MessageBox.Show(myString) confirms.

Yes, you can.

It works great when you have a long SQL string and want to keep it within the
margins of an editor.

Good luck with your project,

Otis Mukinfus

http://www.otismukinfus.com
http://www.arltex.com
http://www.tomchilders.com
http://www.n5ge.com

[=?Utf-8?B?QUEyZTcyRQ==?=]

Thanks Otis.
That is exactly where I have used it, to construct long SQL statements
(without the clutter of continuation line symbols or contatenation as in VB).
I asked the question because I wondered whether I was incurring any penalties
in performance.

[Jon Skeet [C# MVP]]

AA2e72E <AA*****@discussions.microsoft.comwrote:

Thanks Otis.
That is exactly where I have used it, to construct long SQL statements
(without the clutter of continuation line symbols or contatenation as in VB).
I asked the question because I wondered whether I was incurring any penalties
in performance.

No, none whatsoever. On the other hand, you also wouldn't be incurring
any penalties for doing:

string x = "first line"
+"second line"
+"third line";

as that would be done at compile-time.

Where you *would* get penalties (very small, admittedly) would be to
write it as:

string x = "first line";
x += "second line";
x += "third line";

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

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Jon Skeet [C# MVP] wrote:

Where you *would* get penalties (very small, admittedly) would be to
write it as:

string x = "first line";
x += "second line";
x += "third line";

Yes, the performance penalty is small in this case, compared to the time
it will take to make the database call.

It might be worth to mention, however, that you should be careful when
you concatenate strings that way, as it scales very badly. It should
only be used when the number of strings are known beforehand, as the
execution time increases exponentially to an increase in number of strings.

--
Göran Andersson
_____
http://www.guffa.com

[Jon Skeet [C# MVP]]

Göran Andersson <gu***@guffa.comwrote:

Jon Skeet [C# MVP] wrote:

Where you *would* get penalties (very small, admittedly) would be to
write it as:

string x = "first line";
x += "second line";
x += "third line";

Yes, the performance penalty is small in this case, compared to the time
it will take to make the database call.

It might be worth to mention, however, that you should be careful when
you concatenate strings that way, as it scales very badly. It should
only be used when the number of strings are known beforehand, as the
execution time increases exponentially to an increase in number of strings.

Indeed. For more information, see
http://pobox.com/~skeet/csharp/stringbuilder.html

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

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Jon Skeet [C# MVP] wrote:

Göran Andersson <gu***@guffa.comwrote:

>Jon Skeet [C# MVP] wrote:

>>Where you *would* get penalties (very small, admittedly) would be to
write it as:

string x = "first line";
x += "second line";
x += "third line";

Yes, the performance penalty is small in this case, compared to the time
it will take to make the database call.

It might be worth to mention, however, that you should be careful when
you concatenate strings that way, as it scales very badly. It should
only be used when the number of strings are known beforehand, as the
execution time increases exponentially to an increase in number of strings.

Indeed. For more information, see
http://pobox.com/~skeet/csharp/stringbuilder.html

Here's a real life experience, where converting 125 kB of data into a
hex-dump using string concatenation resulted in copying 75 GB (!) of
string data:

http://www.codeproject.com/script/co...=1#xx1519247xx

:)

--
Göran Andersson
_____
http://www.guffa.com