C#中Mdi窗体的问题

Question

我想让子窗体每次打开只显示一次，第一次打开的时候是可以的。但是关闭子窗体再次打开的时候就出现如下的情况了：
子窗体显示代码如下：
  
          public static int rs = 0;//初始化为0
          ReaderSytle RS = new ReaderSytle();//*****控制窗体打开的个数，如果已经打开就不能再打开
            if (rs == 1)
                MessageBox.Show("帮助　窗体已经打开！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Stop);
            else
            {
                RS.MdiParent = this;
                RS.Show();
                rs = 1;
            }

Answer 1

        //查询子窗体是否存在
        private bool CheckChildFrmExist(string childFrmName)
        {
            foreach ( Form childFrm in this.MdiChildren )
            {
                //用子窗体的Name进行判断，如果已经存在则将他激活
                if ( childFrm.Name == childFrmName )
                {
                    if ( childFrm.WindowState == FormWindowState.Minimized )
                        childFrm.WindowState = FormWindowState.Normal;
                    childFrm.Activate();
                    return true;
                }
            }
            return false;
        }

Answer 2

楼上正解， 可以通过  MdiForm.MdiChildren遍历所有子窗体 

Answer 3

这个使用一个类变量就可以了啊：
ReaderSytle RS = null;//在方法外部声明//方法内部代码
{
  if(RS == null || RS.IsDisposed)
  {
    RS = new ReaderSytle();//
  }
  RS.MdiParent = this;
  RS.Show();
}

Answer 4

try
            {
                System.Windows.Forms.Form[] mdiForm = this.MdiChildren;
                bool openFlage = false;
                foreach (Form fr in mdiForm)
                {
                    if (fr.Name == "FcImportRecQuery")
                    {
                        fr.Activate();
                        fr.WindowState = FormWindowState.Maximized;
                        openFlage = true;
                        break;
                    }
                }
                if (!openFlage)
                {
                    Yj_SrvForm.FcImportRecQuery nSG = new Yj_SrvForm.FcImportRecQuery(true);
                    nSG.MdiParent = this;
                    nSG.WindowState = FormWindowState.Maximized;
                    this.Update();
                    nSG.Show();
                }
            }
            catch (Exception exc) { Yj_CommonFunction.ShowMessagebox(exc, this, 0, null); }

Answer 5

没弄明白,是想做个单件吗? 
如果想让窗体在程序中唯一到可以试下下面..       
        private static Form1  _form1 = null;
        private  Form1()
        {
            InitializeComponent();
            
        }
        public static Form1 CreateForm1()
        {
            if (_form1 == null )
            {
              
                _form1 = new Form1();
            }            
            return _form1;
        }
        private void Form1_FormClosed(object sender, FormClosedEventArgs e)
        {
            Form1._form1 = null;    // 如果关闭的话,清空窗体类中的_form1的引用.
        }

Answer 6

修改了一下2楼的算法，关闭再打开一切正常
 private void subForm1ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form2 f2 = new Form2();
            if (CheckChildFrmExist(f2.Name))
            {
                f2.MdiParent = this;
                f2.Show();
            }
            else
            {
                MessageBox.Show("fail");
            }
        }
private void subForm2ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form8 f8 = new Form8();
            if (CheckChildFrmExist(f8.Name))
            {
                f8.MdiParent = this;
                f8.Show();
            }
            else
            {
                MessageBox.Show("fail");
            }
        }        private bool CheckChildFrmExist(string childFrmName)
        {
            bool result = false;
            if (this.MdiChildren.Length >= 1)
            {
                foreach (Form childFrm in this.MdiChildren)
                {
                    //用子窗体的Name进行判断，如果已经存在则将他激活
                    if (childFrm.Name != childFrmName)
                    {
                        if (childFrm.WindowState == FormWindowState.Minimized)
                        {
                            childFrm.WindowState = FormWindowState.Normal;
                        }
                        childFrm.Activate();
                        result = true;
                    }
                    else
                    {
                        result = false;
                        break;
                    }
                    
                }
                return result;
               
            }
            else
            {
                return true;
            }
        }