终于搞定c#中对mdi的操作，代码见内（parent部分）

花了我一上午的时间，找来找去找不到答案，又是急性子，只好自己动手了，见笑，也请大家多提意见，谢了。
parent.cs
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using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
namespace testagain
{
    /// <summary>
    /// Summary description for parent.
    /// </summary>
    public class parent : System.Windows.Forms.Form
    {
        private System.Windows.Forms.MainMenu mainMenu1;
        private System.Windows.Forms.MenuItem m_FileMenu;
        private System.Windows.Forms.MenuItem m_OpenFile;
        private System.Windows.Forms.MenuItem m_Close;
        private System.Windows.Forms.MdiClient mdiClient1;
        private System.Windows.Forms.MenuItem menuItem1;
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.Container components = null;
        public parent()