接口转换

  public interface IA
    {
        void TestA();
    }

    public interface IB
    {
        void TestB();
    }

    public class AB : IA, IB
    {
        public void TestA()
        {
            Console.WriteLine("Test A");
        }

        public void TestB()
        {
            Console.WriteLine("Test B");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            IA aa = Activator.CreateInstance(typeof(AB)) as IA;

            IB bb = aa as IB;
            aa.TestA();
            bb.TestB();
        }
    }