委托+事件的一个小例子

Posted 2020-10-30 有点意思的小Sam

Form2中的输入传到Form1中textBox中：

Form2作为事件发送者：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form2 : Form
    {



        //事件发送者
        public delegate void OnClickHandler(string strMsg);
        public event OnClickHandler OnClickEvent;


        public Form2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (OnClickEvent != null)
            {
                //textBox1.Text.ToString() 是作为事件参数发送到额
                OnClickEvent(textBox1.Text.ToString());
            }
        }
    }
}

Form1是事件接受者：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //事件接受者
        private void button1_Click(object sender, EventArgs e)
        {
            Form2 f2 = new Form2();
            f2.OnClickEvent += new Form2.OnClickHandler(GetText);
            f2.Show();
        }

        private void GetText(string strMsg)
        {
            textBox1.Text = strMsg;
        }
    }
}

 

 

 

另外参考一下网上看到的一个委托和事件的小程序：

“现在我们来编写一个自定义事件的程序。主人养了一条忠实的看门狗，晚上主人睡觉的时候，狗负责看守房子。一旦有小偷进来，狗就发出一个Alarm事件，主人接到Alarm事件后就会采取相应的行动。假设小偷于2009年元旦午夜时分到达。”

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    //事件发送者
    class Dog
    {
        //1.声明关于事件的委托
        public delegate void AlarmEventHandler(object sender, EventArgs e);
        //2.声明事件
        public event AlarmEventHandler Alarm;

        //3.编写引发事件的函数
        public void OnAlarm()
        {
            if (this.Alarm != null)
            {
                Console.WriteLine("Dog Alarm: the thief is coming , worf!");
                this.Alarm(this, new EventArgs());
            }
        }
    }

    //事件接受者
    class Host
    {
        //4.编写事件处理程序
        void HostHandleAlarm(object sender, EventArgs e)
        {
            Console.WriteLine("Host: Catch you!");
        }

        //5.注册事件处理程序
        public Host(Dog dog)
        {
            dog.Alarm += new Dog.AlarmEventHandler(HostHandleAlarm);
        }
    }

    //6.现在来触发事件
    class Program
    {
        static void Main(string[] args)
        {
            Dog dog = new Dog();
            Host host = new Host(dog);

            DateTime now = new DateTime(2008, 12, 31, 23, 59, 50);
            DateTime midnight = new DateTime(2009, 1, 1, 0, 0,0);

            Console.WriteLine("Time flowing...");

            while (now < midnight)
            {
                Console.WriteLine("Time:" + now);
                System.Threading.Thread.Sleep(1000);
                now = now.AddSeconds(1);
            }

            Console.WriteLine("MidNight:" + now);
            Console.WriteLine("The thief is coming...");
            dog.OnAlarm();
            Console.ReadKey();
        }
    }
}