C#不能同时显示多个子窗体

Question

我做了一个MDI的WinForm应用程序，链接access数据库进行数据处理，每个子窗体都有不同的数据和计算功能。我是设置一个窗体为父窗体，然后在应用程序中添加了多个窗体程序，在显示每个窗体程序之前都设置它的MdiParent属性为前面的父窗体，再在父窗体中设置菜单，单击菜单项会打开相应的子窗体。
我的问题是每个子窗体的运行都没有问题，可是当我打开一个子窗体是，再打开另一个子窗体，那前一个窗体就会自动关闭！这是为什么啊？高手指教指教！谢谢了！

Answer 1

这是主窗体的部分代码！   public partial class MainWindow : Form
    {
        public MainWindow()
        {
            InitializeComponent();
        }        File.NewPro newpro;
        Data.DLeftLine leftline;
        Data.LefLinCheck leflincheck;
        LineSurvey.CoorCalcu coorcalcu;
        Data.ChainLine chainline;
        File.OpenPro openpro;
        Data.VerticalLine verticalline;
        public static string tablestr;        private void NewProMenu_Click(object sender, EventArgs e)
        {
            if (newpro == null || newpro.IsDisposed)
            {
                newpro = new URTESS.File.NewPro();
                for (int x = 0; x < this.MdiChildren.Length; x++)
                {
                    Form tempChild = (Form)this.MdiChildren[x];
                    tempChild.Close();
                }
                newpro.MdiParent = this;
                newpro.Show();
            }
        }
        
        private void LefLinDesign_Click(object sender, EventArgs e)
        {
            leftline = new URTESS.Data.DLeftLine();
            tablestr = "左线";
            for (int x = 0; x < this.MdiChildren.Length; x++)
            {
                Form tempChild = (Form)this.MdiChildren[x];
                tempChild.Close();
            }
            
            leftline.MdiParent = this;
            leftline.Show();
        }
        
        private void LefLinCheck_Click(object sender, EventArgs e)
        {
            URTESS.Class.LeftCheckCalcu lefchecal = new URTESS.Class.LeftCheckCalcu();
            lefchecal.CheckCalcu("tb_LeftLine");
            tablestr = "左线";
            leflincheck = new URTESS.Data.LefLinCheck();
            for (int x = 0; x < this.MdiChildren.Length; x++)
            {
                Form tempChild = (Form)this.MdiChildren[x];
                tempChild.Close();
            }
            leflincheck.MdiParent = this;
            leflincheck.Text = "左线参数复核表";
            leflincheck.Show();
        }
       
        private void CooCalcu_Click(object sender, EventArgs e)
        {
            coorcalcu = new URTESS.LineSurvey.CoorCalcu();
            for (int x = 0; x < this.MdiChildren.Length; x++)
            {
                Form tempChild = (Form)this.MdiChildren[x];
                tempChild.Close();
            }
            coorcalcu.MdiParent = this;
            coorcalcu.Show();        }
        
        private void ChainLine_Click(object sender, EventArgs e)
        {
            chainline = new URTESS.Data.ChainLine();
            for (int x = 0; x < this.MdiChildren.Length; x++)
            {
                Form tempChild = (Form)this.MdiChildren[x];
                tempChild.Close();
            }
            chainline.MdiParent = this;
            chainline.Show();
        }        private void RetLinDesign_Click(object sender, EventArgs e)
        {
            leftline = new URTESS.Data.DLeftLine();
            leftline.Text = "右线参数设计表";
            tablestr = "右线";
            for (int x = 0; x < this.MdiChildren.Length; x++)
            {
                Form tempChild = (Form)this.MdiChildren[x];
                tempChild.Close();
            }
            leftline.MdiParent = this;
            leftline.Show();
        }
}

Answer 2

做MDI窗体首先你要将父窗体的IsMDIcontainer属性设为true;然后就是你的事件问题了！
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;namespace WinForm
{
    public partial class Form3 : Form
    {
        public Form3()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            Form1 form1 = new Form1();
            form1.MdiParent = this;
            form1.Show();
        }
        private void button2_Click(object sender, EventArgs e)
        {
            Form2 form2 = new Form2();
            form2.MdiParent = this;
            form2.Show();
        }
    }
}
当单击不同的按钮时就相识不同的窗体！