using System;

public class Program

{

    public static void Main()

    {

        Pop<ClassDescriptor>(new ClassDescriptor());

        Pop<ClassDescriptor>(null);

        Console.WriteLine(typeof(ClassDescriptor).IsSubclassOf(typeof(NullableDescriptor)));

    }

    public static T Pop<T>(object value) {

        Console.WriteLine(typeof(T));

      if (typeof(T).IsSubclassOf(typeof(NullableDescriptor))) {

        Console.WriteLine("is subclass");

      }

      return (T)value;

    }

}

​

public interface NullableDescriptor{}

​

public class ClassDescriptor : NullableDescriptor{}