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

Question

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?

This does not seem to be possible at the moment, plase see the first comment [here](http://stackoverflow.com/q/3720222/303290) — Paul Kertscher, Jul 28 '17 at 06:32
While the linked duplicate cites the specification, there is a way around it, declare `ID` in the outer namespace and `CC` in an inner namespace. The fact that they're in the same namespace is the problem here. — Lasse V. Karlsen, Jul 28 '17 at 06:46

score 0 · Answer 1 · answered Jul 28 '17 at 06:30

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).

score -1 · Answer 2 · answered Jul 28 '17 at 06:31

-1

Don't use an alias.

public class C<T> {
   T id;
}

...

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

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

answered Jul 28 '17 at 06:31

tymtam

2 Answers2