What does placing a @ in front of a C# variable name do?
C#C# Problem Overview
I've been working with some C# legacy code and I've been seeing a lot of @ symbols in front of variable names. What does this signify or do?
Currently I'm seeing it a lot in front of variables with common names that aren't reserved. E.g.:
MyProcedure(@step.LoadInstanceId, @step.ResultCode, @step.StatusCode);
Given that step isn't a reserved word, is there any reason that they should be escaped?
C# Solutions
Solution 1 - C#
It's just a way to allow declaring reserved keywords as vars.
void Foo(int @string)
Solution 2 - C#
It allows you to use a reserved word, like 'public' for example, as a variable name.
string @public = "foo";
I would not recommend this, as it can lead to unecessary confusion.
Solution 3 - C#
Putting @ in front of a string tells the compuler not to process escape sequences found within the string.
From the documentation:
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.
Another use of the @ symbol is to use referenced (/reference) identifiers that happen to be C# keywords. For more information, see 2.4.2 Identifiers.
Solution 4 - C#
This escapes reserved words in C#.
Solution 5 - C#
The @ sign is used with identifiers that are the same as language keywords. There are two main uses for this
- interoperating with non-C# code. In languages like VB or IronPython the keywords are not the same as in C# and they may have declared classes and properties with names that match C# keywords. If this feature was not present this code would not be accessible in C#.
- machine generated code. If a code generator generates code based on some external source (for example WSDL) the generator can just prefix all identifiers with @ and not check and convert identifiers that match C# keywords.
Are you sure that your case is not the second?
Solution 6 - C#
The original question asks for a reason why one would escape a not-reserved word. What comes to my mind is that if step would become a reserved word in future the code example would still compile. I guess it is also a valid option for code generators.