Parse classes to interface that can inherit

See more:

C#

inheritance

parsing

Hey i was here to day playing around with interfaces to try get better to them (cos i never use anything but abstract classes cos i never feel interfaces is much of use) but i have made the following code:

class Program
    {
        static void Main(string[] args)
        {
            List<maintestclass> tl = new List<maintestclass>() { new testclass(), new testclass(), new testclass2()};
            List<testinterface> ti = new List<testinterface>();

            Console.ReadLine();
        }
    }

    public class testclass : maintestclass, testinterface
    {
        public void testmetode()
        {
            Console.WriteLine("interface call");
        }
    }

    public class testclass2 : maintestclass
    {
    }

    public abstract class maintestclass
    {

    }

    public interface testinterface
    {
        void testmetode();
    }

and what i really wanna do is to parse every object in "tl" that can inherit from testinterface to ti but it seems i cant make it to work, i've tried to use "where" and get type but cant find a usefull way to do it...

if anyone fast could help me i would be greatfull. (sample codes would help alot)

- Jackie