Get the type of the Generic parameter

Question

I have the following classes

public interface InterfaceBase
{
}

public class ImplementA:InterfaceBase
{
}

public class ImplementB:InterfaceBase
{
}

public void TestImplementType<T>(T obj) where T: InterfaceBase
{
}

How to infer what the T is whether ImplementA or ImplementB? I tried to use

typeof(T) is ImplementA

but this expression is always evaluated to false.

Edit: And how am I going to cast obj to ImplementA or ImplementB?

Answer 1

obj is ImplementA

Answer 2

How about:

 if(obj.GetType().Equals(typeof(ImplementA)))
 {
   // ...
 }

Answer 3

typeof(T) returns the Type of T - and System.Type doesn't implement ImplementA. What you want is:

if (typeof(ImplementA).IsAssignableFrom(typeof(T))
{
}

Answer 4

Strictly, you should avoid too much specialization within generics. It would be cleaner to put any specialized logic in a member on the interface, so that any implementation can do it differently. However, there are a number of ways:

You can test "obj" (assuming it is non-null)

    bool testObj = obj is ImplementA;

You can test T for being typeof(ImplementA):

    bool testEq = typeof(T) == typeof(ImplementA);

Likewise you can test it for being ImplementA or a subclass:

    bool testAssign = typeof(ImplementA).IsAssignableFrom(typeof(T));