C#インタフェースマルチステートインスタンス

//    ，define interface
    interface IAction
    {
        string Act();
    }
    /// 

    ///  A    ，class a inherit interface IAction
    /// 
    class InterfaceTest :IAction
    {
        public string Act()
        {
            return "this class a.Act";
        }
    }
    /// 

    ///  B    ，class a inherit interface IAction
    /// 
    class Bclass : IAction
    {
        public string Act()
        {
            return "this class b.Act";
        }
    }
    /// 

    ///  C     IAction     ，class C set the interface as parameter
    /// 
    class Cclass
    {
        public string CallFun(IAction action)
        {
            return action.Act();
        }
    }

//    ，instantiate
InterfaceTest aclass = new InterfaceTest();
Bclass bclass = new Bclass();
Cclass cclass = new Cclass();
//              ，use the class as parameter to call different functions
MessageBox.Show(cclass.CallFun(bclass)+"
"+ cclass.CallFun(aclass));