急求: C# 中关于MDI的问题

如下红字体的就我要问大家的,帮帮我using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
 
namespace CopyERP
{
    public partial class PgMenu : Form
    {
        public PgMenu()
        {
            InitializeComponent();
        }
 
        //-------------------------------------------------------------------------
        //判断Child WD 是否已经打开
        //-------------------------------------------------------------------------
        private bool checkChildFrmExist(string childFrmName)
        {
            
 
            foreach (Form   childFrm    in this.MdiParent.MdiChildren)
            {
                if (childFrm.Name == childFrmName) //用子窗体的Name进行判断，如果存在则将他激活
                {
                    if (childFrm.WindowState == FormWindowState.Minimized)
                    {
                        childFrm.WindowState = FormWindowState.Normal;
                    }
 
                    childFrm.Activate();
                    return true;
                }
            }
           
            return false;
        }
         //-------------------------------------------------------------------------
        //PgMenu_Load载入，项目载入节点
        //-------------------------------------------------------------------------
        private void PgMenu_Load(object sender, EventArgs e)
        {
            DataRow myRow;
             // TODO: 这行代码将数据加载到表“dS_Load.sy010m”中。您可以根据需要移动或移除它。
            this.sy010mTableAdapter.Fill(this.dS_Load.sy010m);
             for (int i = 0; i < dS_Load.Tables["sy010m"].Rows.Count; i++)
            {
                myRow = dS_Load.Tables["sy010m"].Rows[i];
                string ls_module = myRow[0].ToString().Trim();
                string ls_module_f = myRow[0].ToString().Trim().Substring(0, 4);
                string ls_module_l;
                string ls_module_t;
                string ls_nm_cha = myRow[3].ToString().Trim();
 
                if (ls_module.Substring(4, 4) == "0000")
                {
                    TreeNode tn_1 = new TreeNode();
                    tn_1.Name = ls_module;
                    tn_1.Text = ls_nm_cha;
                    treeView1.Nodes.Add(tn_1);
 
                }   //if
                else
                {
                    for (int j = 0; j < treeView1.Nodes.Count; j++)
                    {
                        //MessageBox.Show(treeView1.Nodes[j].Name.ToString());
                        ls_module_t = treeView1.Nodes[j].Name.ToString().Substring(0, 4);
                        ls_module_l = treeView1.Nodes[j].Name.ToString().Substring(4, 4);
                        if (ls_module_f == ls_module_t && ls_module_l == "0000")
                        {
                            TreeNode tn_2 = new TreeNode();
                            tn_2.Name = ls_module;
                            tn_2.Text = ls_nm_cha;
                            treeView1.Nodes[j].Nodes.Add(tn_2);
                        }
                    }   //for
                }  //else
             }   //for
         }
         //-------------------------------------------------------------------------
        //查询节点下的程序目录
        //-------------------------------------------------------------------------
        private void treeView1_AfterSelect(object sender, TreeViewEventArgs e)
        {
            string ls_name;
            ls_name = treeView1.SelectedNode.Name;
            this.sy020mTableAdapter.Fill(this.dS_Load.sy020m, ls_name);
        }
         //-------------------------------------------------------------------------
        //双击Dgv_menu 程序项目事件
        //-------------------------------------------------------------------------
        private void dgv_menu_CellDClick(object sender, DataGridViewCellEventArgs e)
        {
            string ls_pgid;
            ls_pgid = this.dgv_menu.CurrentRow.Cells[0].Value.ToString().Trim();
              ／／如何通过ls_pgid 来打开我想的那个程序，帮帮我
 
        }
 
        //-------------------------------------------------------------------------
    }
 }