委托传值

点击Form1的按钮，把文本框的值传给Form2。再点击Form2的按钮，把文本框的值传给Form1。

Form1代码：

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

namespace 委托传值
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btn1_Click(object sender, EventArgs e)
        {
            Form2 frm2 = new Form2(txt1.Text,doSth);//Form2构造方法
            frm2.Show();
        }
        //把窗体2的字符串给窗体1
        public void doSth(string msg)
        {
            txt1.Text = msg;
        }
    }
}

Form2的代码：

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

namespace 委托传值
{
    public delegate void MyDel(string str);//定义委托
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();//初始化窗体
        }
        private MyDel _del;//实例化委托
        public Form2(string str,MyDel del)
        {
            InitializeComponent();//初始化窗体
            txt2.Text = str;
            this._del = del;//构造方法传参
        }
        private void Form2_Load(object sender, EventArgs e)
        {

        }

        private void btn2_Click(object sender, EventArgs e)
        {
            //调用委托前先判定
            if (this._del != null)
            {
                this._del(txt2.Text);//调用委托
                
            }
            this.Close();
        }
        
    }
}