What's the use/meaning of the @ character in variable names in C#?

Question

I discovered that you can start your variable name with a '@' character in C#. In my C# project I was using a web service (I added a web reference to my project) that was written in Java. One of the interface objects defined in the WSDL had a member variable with the name "params". Obviously this is a reserved word in C# so you can't have a class with a member variable with the name "params". The proxy object that was generated contained a property that looked like this:

public ArrayList @params {
    get { return this.paramsField; }
    set { this.paramsField = value; }
}

I searched through the VS 2008 c# documentation but couldn't find anything about it. Also searching Google didn't give me any useful answers. So what is the exact meaning or use of the '@' character in a variable/property name?

Answer 1

It just lets you use a reserved word as a variable name. Not recommended IMHO (except in cases like you have).

Answer 2

It simply allows you to use reserved words as variable names. I wanted a var called event the other day. I was going to go with _event instead, but my colleague reminded me that I could just call it @event instead.

Answer 3

In C# the at (@) character is used to denote literals that explicitly do not adhere to the relevant rules in the language spec.

Specifically, it can be used for variable names that clash with reserved keywords (e.g. you can't use params but you can use @params instead, same with out/ref/any other keyword in the language specification). Additionally it can be used for unescaped string literals; this is particularly relevant with path constants, e.g. instead of path = "c:\temp\somefile.txt" you can write path = @"c:\temp\somefile.txt". It's also really useful for regular expressions.

Answer 4

Straight from the C# Language Specification, § 2.4.2 Identifiers (C#) :

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.

Answer 5

If we use a keyword as the name for an identifier, we get a compiler error “identifier expected, ‘Identifier Name’ is a keyword” To overcome this error, prefix the identifier with “@”. Such identifiers are verbatim identifiers. 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