WinFrom 窗体内嵌子窗体

需要展示的效果如下

Form1代码如下：

using System;
using System.Windows.Forms;

namespace Winfrom技巧
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.IsMdiContainer = true;
        }

        private void 窗体2ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form2 frm2 = new Form2();
            frm2.MdiParent = this;
            frm2.Show();
            
        }

        private void 窗体3ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form3 frm3 = new Form3();
            frm3.MdiParent = this;
            frm3.Show();
        }
    }
}