MDI 窗口的创建

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 MDI
{
    public partial class FormMain : Form
    {
        public FormMain()
        {
            InitializeComponent();
            
        }

        private void 新建NToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form fr1 = new Form();
            fr1.MdiParent = this;
            fr1.Show();
        }

        private void 打开OToolStripMenuItem_Click(object sender, EventArgs e)
        {
            FormMDI1 frmMDI1 = new FormMDI1();
            frmMDI1.MdiParent = this;
            frmMDI1.Show();

            FormMDI2 frmMDI2 = new FormMDI2();
            frmMDI2.MdiParent = this;
            //frmMDI2.Owner = this;
            frmMDI2.Show();

            FormMDI3 frmMDI3 = new FormMDI3();
            frmMDI3.MdiParent = this;
            frmMDI3.Show();
        }

        private void FiletoolStripMenuItem1_Click(object sender, EventArgs e)
        {
            LayoutMdi(MdiLayout.Cascade);
        }

        private void NewStripMenuItem2_Click(object sender, EventArgs e)
        {
            LayoutMdi(MdiLayout.TileHorizontal);
        }

        private void 垂直排列ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            LayoutMdi(MdiLayout.TileVertical);
        }

        private void 退出XToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.Close();
            this.Dispose();
        }
    }
}