委托和委托链

1.委托

　　委托是一种类型，是方法的类型，委托定义了方法的类型；这样就能把方法作为参数进行传递。

namespace First
{
    //定义委托，它定义了可以代表方法的类型
    public delegate void GreetingDelegate(string name);

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void GreetPeople(string name, GreetingDelegate MakeGreeting)
        {
            MakeGreeting(name); //此句的意思是将name传递给方法MakeGreeting
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //将方法EnglishGreeting作为一个参数传递
            //对应到GreetPeople中，是将"KIMI"传递给了EnglishGreeting
            GreetPeople("KIMI", EnglishGreeting);
            //将方法ChineseGreeting作为一个参数传递
            //对应到GreetPeople中，是将"莱科宁"传递给了ChineseGreeting
            GreetPeople("莱科宁", ChineseGreeting);
        }

        //此处函数的签名必须和委托GreetingDelegate(string name)一致
        private void EnglishGreeting(string name)
        {
            MessageBox.Show("Morning, " + name);
        }
        private void ChineseGreeting(string name)
        {
            MessageBox.Show("早上好，" + name);
        }
    }
}

运行结果：

陆续跳出两个对话框

 2.委托链

　　将多个方法捆绑到同一个委托对象上，形成委托链，当调用这个委托对象时，将依次调用委托链中的方法。

//定义委托，它定义了可以代表方法的类型
    public delegate void GreetingDelegate(string name);

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void GreetPeople(string name, GreetingDelegate MakeGreeting)
        {
            MakeGreeting(name); //此句的意思是将name传递给方法MakeGreeting
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //将方法EnglishGreeting作为一个参数传递
            //对应到GreetPeople中，是将"KIMI"传递给了EnglishGreeting
            //GreetPeople("KIMI", EnglishGreeting);
            //将方法ChineseGreeting作为一个参数传递
            //对应到GreetPeople中，是将"莱科宁"传递给了ChineseGreeting
            //GreetPeople("莱科宁", ChineseGreeting);
            GreetingDelegate delegate1 = new GreetingDelegate(EnglishGreeting);
            //delegate1 = ChineseGreeting;
            delegate1 += ChineseGreeting;
            //delegate1 += EnglishGreeting;
            delegate1("KIMI");
        }

        //此处函数的签名必须和委托GreetingDelegate(string name)一致
        private void EnglishGreeting(string name)
        {
            MessageBox.Show("Morning, " + name);
        }
        private void ChineseGreeting(string name)
        {
            MessageBox.Show("早上好，" + name);
        }
    }

运行结果：

　　依次弹出两个对话框