C# 中变量名中@ 字符的用途/含义是什么？
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What's the use/meaning of the @ character in variable names in C#?
提问by Remko Jansen
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:
我发现您可以在 C# 中以“@”字符开头变量名。在我的 C# 项目中，我使用了一个用 Java 编写的 Web 服务（我向我的项目添加了一个 Web 引用）。WSDL 中定义的接口对象之一具有名为“params”的成员变量。显然，这是 C# 中的保留字，因此您不能拥有具有名称为“params”的成员变量的类。生成的代理对象包含一个如下所示的属性：
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?
我搜索了 VS 2008 c# 文档，但找不到任何相关信息。搜索谷歌也没有给我任何有用的答案。那么变量/属性名称中“@”字符的确切含义或用法是什么？
采纳答案by Atif Aziz
Straight from the C# Language Specification, Identifiers (C#):
直接来自C# Language Specification, 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.
前缀“@”允许使用关键字作为标识符，这在与其他编程语言交互时非常有用。字符@ 实际上不是标识符的一部分，因此标识符在其他语言中可能被视为普通标识符，没有前缀。带有@ 前缀的标识符称为逐字标识符。
回答by rslite
It just lets you use a reserved word as a variable name. Not recommended IMHO (except in cases like you have).
它只是让您使用保留字作为变量名。不推荐恕我直言（除非像你这样的情况）。
回答by Mark Embling
It simply allows you to use reserved words as variable names. I wanted a var called eventthe other day. I was going to go with _eventinstead, but my colleague reminded me that I could just call it @eventinstead.
它只是允许您使用保留字作为变量名。前event几天我想要一个 var 。我本来打算去的_event，但我的同事提醒我，我可以直接打电话给它@event。
回答by Tomer Gabel
In C# the at (@) character is used to denote literals that explicitly do not adhere to the relevant rules in the language spec.
在 C# 中，at (@) 字符用于表示明确不遵守语言规范中相关规则的文字。
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.
具体来说，它可以用于与保留关键字冲突的变量名（例如，您不能使用 params 但您可以使用 @params 代替，与语言规范中的 out/ref/任何其他关键字相同）。此外，它还可以用于未转义的字符串文字；这与路径常量特别相关，例如，path = "c:\\temp\\somefile.txt"您可以编写path = @"c:\temp\somefile.txt". 它对于正则表达式也非常有用。
回答by Atif Aziz
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
如果我们使用关键字作为标识符的名称，则会出现编译器错误“预期标识符，'标识符名称'是关键字”要克服此错误，请在标识符前加上“@”。这样的标识符是逐字标识符。字符@ 实际上不是标识符的一部分，因此标识符在其他语言中可能被视为普通标识符，没有前缀
回答by Colonel Panic
Unlike Perl's sigils, an @prefix before a variable name in C# has no meaning. If xis a variable, @xis another name for the same variable.
与 Perl 的 sigils 不同@，C# 中变量名前的前缀没有意义。如果x是变量，@x则是同一变量的另一个名称。
> string x = "abc";
> Object.ReferenceEquals(x, @x).Dump();
True
But the @prefix does have a use, as you've discovered - you can use it to clarify variables names that C# would otherwise reject as illegal.
但是@前缀确实有用途，正如您所发现的 - 您可以使用它来阐明 C# 否则会拒绝为非法的变量名称。
> string string;
Identifier expected; 'string' is a keyword
> string @string;
回答by BartoszKP
Another use case are extension methods. The first, special parameter can be distinguished to denote its real meaning with @thisname. An example:
另一个用例是扩展方法。第一个，特殊参数可以通过@this名称来区分以表示其真正含义。一个例子：
public static TValue GetValueOrDefault<TKey, TValue>(
this IDictionary<TKey, TValue> @this,
TKey key,
TValue defaultValue)
{
if ([email protected](key))
{
return defaultValue;
}
return @this[key];
}
回答by Mina Gabriel
You can use it to use the reserved keywords as variable name like
您可以使用它来使用保留关键字作为变量名，如
int @int = 3;
the compiler will ignores the @and compile the variable as int
编译器将忽略@变量并将其编译为int
it is not a common practice to use thought
使用思想不是一种常见的做法
回答by Umar Abbas
The @symbol allows you to use reserved keywords for variable name. like @int, @string, @doubleetc.
该@符号允许您使用保留关键字作为变量名。像@int，@string，@double等等。
For example:
例如：
string @public = "Reserved Keyword used for me and its fine";
The above code works fine, but below will not work:
上面的代码工作正常，但下面的代码不起作用：
string public = "This will not compile";
