When Is it Better To Use @ Before a String?

Question

In code that declares or uses a string, I usually see the developers declare it like this:

string randomString = @"C:\Random\RandomFolder\ThisFile.xml";

Instead of:

string randomString = "C:\\Random\\RandomFolder\\ThisFile.xml";

That's the only thing that I see which is better to use the @ prefix, since you don't need to do \\, but is there any other use for it when it's better than just without it?

Cimah

Answer 1

The @ sign indicates to the compiler that the string is a verbatim string literal, and thus does not require you to escape any of the characters. Not just the backslash, of course. No escape sequences of any kind are processed by the compiler.

Whether it's "better" or not is an extremely difficult question to answer. This is a purely stylistic choice. Some might argue that the string contents are more readable when you use a string literal, rather than having to escape all of the characters. Others might prefer consistency, where all strings that contain characters that would ordinarily require escaping would have to be escaped. This makes it easier to notice errors in code at a glance. (For what it's worth, I fall into the latter camp. All my paths have \\.)

That being said, it's extremely convenient for regular expressions, for which you'd otherwise be escaping all over the place. And since they don't look much like regular strings, there's minimal risk of confusion.

Simonasimonds

Agreed, since C# is a subset of C which is designed for UNIX paths where the forward slash character is used as the path separator, the backslash character is used as an escape character. Why microsoft chose the backslash character as their path separator is an odd question, especially given that windows explorer is "mystically tied" to IE, which of course also uses UNIX paths for URLs. Only when using paths and debugging under windows do I use this litteral. Other than that it is usually agreed that paths should not be hardcoded. So yeah, anytime you need a string w/ lots of backslashes. – Ganges

Answer 2

Windows path names aren't the only things with a lot of backslashes. For instance, @-strings are very useful for regular expressions because they avoid having to double-escape everything.

They can also span multiple lines, so if you ever end up having to have multi-line strings in your code, they make it a bit more convenient.

Carruthers

Answer 3

Makes Regex simpler

@"^(([\w-]+\.)+[\w-]+|([a-zA-Z]{1}|[\w-]{2,}))((([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])){1}|([a-zA-Z]+[\w-]+\.)+[a-zA-Z]{2,4})$";

Multiple lines string

string s = @"testing
some

string with multiple
lines";

Diaphane

Answer 4

It is especially useful for regular expressions that involve matching a backslash character explicitly. Since this is a special character in both C# strings syntax and regex syntax, it requires "double escaping". Example:

string regex = "\\\\.*\\.jpg"

Same expression using the @-notation would be more tidy:

string regex = @"\\.*\.jpg"

Pericarditis

Answer 5

"" and @"" are both string literals, first is regular literal but the latter is a verbatim string literal '@' prefix before any string in C# .NET (Regular string literal and Verbatim string literal in C#.NET)

Internment