How to use an alias type as a generic type parameter in C# [duplicate]

问题

This question already has answers here:

Why can one aliased C# Type not be accessed by another? (3 answers)

Closed 2 years ago.

How do you pass an alias type defined by using to the generic class?

I tried the following code:

using ID = Int32; // it might be replaced with `String`.
using CC = C<ID>;

public class C<T> {
    T id;
}

and there will be an error:

Error CS0246 The type or namespace name 'ID' could not be found (are you missing a using directive or an assembly reference?)

But the using directive is right above the line where the error occurs. Did I miss something?

回答1:

I do not really know what you are trying to achieve with this, but you can, however, do something similar with inheritance

public class CC : C<ID>
{
}

The class CC will derive from C<T> with a concrete type. Hence CC.T will be of type Int32 (or whatever).

回答2:

Don't use an alias.

public class C<T> {
   T id;
}

...

void Foo() {
  var x = new C<Int32>();

  var y = new C<string>();
}

来源：https://stackoverflow.com/questions/45366303/how-to-use-an-alias-type-as-a-generic-type-parameter-in-c-sharp