C＃的“ nameof”运算符的源代码

Question

Where can I get the source code for "nameof" of C# or how do I decompile it?

I checked https://referencesource.microsoft.com/ , but I couldn't find it.

Answer 1

It's not something you can decompile as such, or show you source code for. It's part of the C# compiler: when you use nameof(Foo) the compiler just injects "Foo" into the source code. The IL for the methods is exactly the same:

static void PrintMyName()
{
    Console.WriteLine(nameof(PrintMyName));
}

vs

static void PrintMyName()
{
    Console.WriteLine("PrintMyName");
}

As noted in comments, it's not just that the name is taken literally as per the operand; it's the last part of the name that's used. So for example, if you have:

string x = "10";
string text = nameof(x.Length);

then that will resolve to "Length". (This doesn't use the value of x at execution time, either - it's fine if x is null. Or you could use nameof(string.Length) or nameof(String.Length) .)

Answer 2

nameof is a keyword, so you would need to look into the compiler for the source code of how it is processed. Fortunately for you, the C# compiler is now open-sourced under the Roslyn project. Understanding a compiler is not a trivial task – source code is passed through pipelines of transformations, which each one adding more syntactic or semantic information. To start you off, the GetContextualKeywordKind parses the nameof keyword into a SyntaxKind.NameOfKeyword , which then gets matched in TryBindNameofOperator .

As to your other question of creating another such operator: Yes, you can, by cloning and modifying the Roslyn source. However, your new operator would obviously only work on the modified compiler, so you'd need to supply this to whoever will be compiling your code. This is something that's rarely done; you're normally better off defining extension methods for your custom functionality, unless you need something particularly esoteric.