委托列子

  public  class card
    {
        public delegate void shua(object txt);
        public event shua shuashijian;



        public void yanzheng(string num, object txt)
        {
            if (num == "123")
            {
                if (shuashijian != null)
                {
                    shuashijian(txt);
                }
            }
        }
    }

public class shitang
    {
        public shitang(card m)
        {
            m.shuashijian += new card.shua(ob);
        }
        public void ob(object txt)
        {
            ((TextBox)txt).Text = "吃饭";
        }

    }

        private void button1_Click(object sender, EventArgs e)
        {
            card m = new card();
            shitang s = new shitang(m);
            m.yanzheng("123", textBox1);
        }