How to learn whether an interface is derived from a specific interface?

Question

Hi,

I have an interface like that:

 public interface IViewA : IViewB, IViewC
 {
    byte prop { get; set; }
 }

and I have a generic method like that:

public void OpenPopup<T>(WindowState state)
{
    if ((typeof(T) as IViewC)!=null)
    {
         //Process A
    }
    else
    {
        //Process B
    }

}

Although I send T as an interface which derives from IViewC, Process A is not being processed.

So how to learn at runtime via reflection whether an interface derives from other interface?

thanks

Answer 1

Instead of typeof use isAssignableFrom.

Answer 2

Try the following

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

Answer 3

if ((typeof(T) as IViewC)!=null)

This is wrong. What you wrote tests whether the Type object returned by typeof(T) is an IViewC, which it obviously isn't.

You want:

if (typeof(IViewC).IsAssignableFrom(typeof(T))

Answer 4

Try something like typeof(IViewC).IsAssignableFrom(typeof(T)).

Right now you're trying to treat typeof(T), which is a System.Type as IViewC, which will not work.

Answer 5

typeof(T) as IViewC is completely wrong. You are trying to cast from Type to IViewC, which will always fail, always resulting in null.

You want typeof(T).GetInterfaces(), and look through the returned list to see if your interface is in there.