private void Form1_Load(object sender, EventArgs e)//Form加载事件
        {
            //result获得对话框的返回值
            DialogResult result = MessageBox.Show("是否打开窗体", "提示", MessageBoxButtons.OK, MessageBoxIcon.Question);//显示具有文本，标题，按钮，图标（从左到右排列）的消息框
            if (result == DialogResult.OK)
                this.Show();

        }
//Form激活事件
        private void Form1_Activated(object sender, EventArgs e)
        {
            //MessageBox.Show("窗体激活！");
            //窗体激活时触发这个事件，因为窗体一直处于激活状态，可以用于数据库中控件的重新绑定数据
        }
//关闭Form事件
        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            DialogResult result = MessageBox.Show("是否关闭窗体", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Warning);
            if (result == DialogResult.OK)
            {
                e.Cancel = false;//指示不应该取消事件，继续关闭
            }
            else if (result == DialogResult.Cancel)
            {
                e.Cancel = true;//指示取消事件，停止关闭
            }
        }
//Form窗体间的调用
        private void button1_Click(object sender, EventArgs e)
        {
            Form2 f2 = new Form2();
            f2.ShowDialog();//以对话框的方式显示窗体，它为模式窗体，此时form1（其他窗体）看不到，如果是show方法，两个窗体都可以看到
            //f2.Hide();//隐藏窗体，它所占用的资源并没有释放掉
        }

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 WindowsFormsApplication6
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
//将子窗体都显示出来
        private void 显示ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form2 f2 = new Form2();
            f2.MdiParent = this;
            f2.Show();
            Form3 f3 = new Form3();
            f3.MdiParent = this;
            f3.Show();
            Form4 f4 = new Form4();
            f4.MdiParent = this;
            f4.Show();
        }

        private void 水平排列ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            LayoutMdi(MdiLayout.TileHorizontal);//水平排列子窗体
        }

        private void 垂直排列ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            LayoutMdi(MdiLayout.TileVertical);//垂直排列子窗体

 } private void 层叠排列ToolStripMenuItem_Click(object sender, EventArgs e)
 { 
LayoutMdi(MdiLayout.Cascade);// 层叠排列子窗体

 } 
} 
}