using System;

​

class Program

{

    interface IObject<in A>

    {

        string typeOf();

    }

    class samlpe<A> : IObject<A>

    {

​

        string IObject<A>.typeOf()

        {

            return typeof(A).ToString();

        }

    }

    class samlpeB<A> : IObject<A>

    {

​

        string IObject<A>.typeOf()

        {

            return typeof(A).ToString();

        }

    }

​

​

    static void Main(string[] args)

    {

        IObject<object> _object = new samlpe<Object>();

        IObject<string> _string = new samlpeB<String>();

        _string = _object ;//可以轉換成子型別

    }     

}