为什么此表达式有效？ （C＃6.0）

Question

nameof(ServiceResult<object>.Result) , where ServiceResult<object> is my custom type and Result is the field of this type. ServiceResult<object> is just a declaration of type, it doesn't have operator new and (), but official page of MS says nameof accepts variable and its members. Why this expression works? I didn't see such declarations before.

Answer 1

The spec you mentioned is probably an old one, C# 6.0 nameof operator reference:

https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/nameof

The argument to nameof must be a simple name, qualified name, member access, base access with a specified member, or this access with a specified member. The argument expression identifies a code definition, but it is never evaluated.

In your case, it's an expression. Similar to

nameof(C.Method2) -> "Method2"

from the examples list in that article.

Examples

using Stuff = Some.Cool.Functionality  
class C {  
    static int Method1 (string x, int y) {}  
    static int Method1 (string x, string y) {}  
    int Method2 (int z) {}  
    string f<T>() => nameof(T);  
}  

var c = new C()  

nameof(C) -> "C"  
nameof(C.Method1) -> "Method1"   
nameof(C.Method2) -> "Method2"  
nameof(c.Method1) -> "Method1"   
nameof(c.Method2) -> "Method2"  
nameof(z) -> "z" // inside of Method2 ok, inside Method1 is a compiler error  
nameof(Stuff) = "Stuff"  
nameof(T) -> "T" // works inside of method but not in attributes on the method  
nameof(f) -> "f"  
nameof(f<T>) -> syntax error  
nameof(f<>) -> syntax error  
nameof(Method2()) -> error "This expression does not have a name"