abstract class Implementor
    {
        public abstract void Operation();
    }

class AImplementor : Implementor
    {
        public override void Operation()
        {
            Console.WriteLine("AImplementor的方法执行");
        }
    }

class BImplementor : Implementor
    {
        public override void Operation()
        {
            Console.WriteLine("BImplementor的方法执行");
        }
    }

class Abstraction
    {
        protected Implementor implementor;

        public void SetImplementor(Implementor implementor)
        {
            this.implementor = implementor;
        }

        public virtual void Operation()
        {
            implementor.Operation();
        }

    }

class AAbstraction : Abstraction
    {
    }

Abstraction obj = new AAbstraction();
            obj.SetImplementor(new AImplementor());
            obj.Operation();
            obj.SetImplementor(new BImplementor());
            obj.Operation();