委托-窗口简单练习

1,共有两个窗体

 主窗体代码

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

namespace 委托应用
{
    //主窗体接受信息委托
    public delegate void ReturnText(string info);
    //主窗体发送信息委托
    public delegate void SendText(string info);

    public partial class FormMain : Form
    {
        public FormMain()
        {
            InitializeComponent();
        }
        //创建一个集合用于储存子窗体
        public List<Form> forms = new List<Form>();
        //根据接受委托创建方法
        public void ReturnTextMethod(string info)
        {
            this.textBox1.Text = info;
        }
        //主窗体发送信息变量
        public SendText sendText;
        //创建子窗体
        private void button3_Click(object sender, EventArgs e)
        {
            //为了防止重复的建立子窗体
            if (forms.Count==0)
            {
                //创建3个子窗体
                for (int i = 1; i < 4; i++)
                {
                    FormChild child = new FormChild();
                    //这里需要设置子窗体的StartPosition属性为Manual
                    child.Location = new Point(250 * i, 200);
                    //子窗体中的委托变量关联主窗体的方法
                    child.returnText += this.ReturnTextMethod;
                    sendText += child.SendText;
                    forms.Add(child);
                    child.Show();
                }
            }


        }
        //关掉所有子窗体
        private void button4_Click(object sender, EventArgs e)
        {
            foreach (var item in forms)
            {
                item.Close();               
            }
            //清空集合
            forms.Clear();
        }
        //主窗体发送信息
        private void button1_Click(object sender, EventArgs e)
        {
            sendText(this.textBox2.Text);
        }
    }
}

子窗体代码

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

namespace 委托应用
{
    public partial class FormChild : Form
    {
        //子窗体发送信息变量
        public ReturnText returnText;
        public FormChild()
        {
            InitializeComponent();
        }
        //
        public void SendText(string info)
        {
            this.textBox2.Text = info;
        }
        private void button1_Click(object sender, EventArgs e)
        {
            returnText(this.textBox1.Text);
        }
    }
}