例一：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace VirtualMethod
{
    class Program
    {
        static void Main(string[] args)
        {
            Base b1 = new Derived();
            b1.Start();//输出什么？
            b1.Stop();//输出什么？
            b1.Turn();//输出什么？
        }
    }

    public interface IVehicle
    {
        void Start();
        void Stop();
        void Turn();
    }

    public class Base : IVehicle
    {
        public void Start()
        {
            Console.WriteLine("a");
        }

        public void Stop()
        {
            Console.WriteLine("b");
        }

        public void Turn()
        {
            Console.WriteLine("c");
        }
    }

    public class Derived : Base, IVehicle
    {
        void IVehicle.Start()
        {
            Console.WriteLine("d");
        }
        public void Stop()
        {
            Console.WriteLine("e");
        }

        public void Turn()
        {
            Console.WriteLine("f");
        }
    }
}

例二：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace VirtualMethod
{
    class Program
    {
        static void Main(string[] args)
        {
            ReallyDerived r1 = new ReallyDerived();
            Derived r2 = r1;
            Base r3 = r1;
            ICommon r4 = r1;

            r1.Doit();//输出什么？
            r2.Doit();//输出什么？
            r3.Doit();//输出什么？
            r4.Doit();//输出什么？
        }
    }

    public interface ICommon
    {
        void Doit();
    }

    public class Base : ICommon
    {
        void ICommon.Doit() { Console.WriteLine("a"); }
        public virtual void Doit() { Console.WriteLine("b"); }
    }

    public class Derived : Base, ICommon
    {
        void ICommon.Doit() { Console.WriteLine("c"); }
        public new virtual void Doit() { Console.WriteLine("d"); }
    }

    public class ReallyDerived : Derived
    {
        public override void Doit() { Console.WriteLine("e"); }
    }

}