正在阅读：MDI应用中的单实例(singleton)窗口MDI应用中的单实例(singleton)窗口

private void toolBar1_ButtonClick(object sender,
     System.Windows.Forms.ToolBarButtonClickEventArgs e)
{
    // a flag to store if the child form is opened or not
    bool found = false;
 
    if (e.Button == toolBarButton1)
    {
       // get all of the MDI children in an array
       Form[] charr = this.MdiChildren;
 
       if (charr.Length == 0)      // no child form is opened
       {
          Patients myPatients = new Patients();
          myPatients.MdiParent = this;
          // The StartPosition property is essential
          // for the location property to work
          myPatients.StartPosition = FormStartPosition.Manual;
          myPatients.Location = new Point(0,0);
          myPatients.Show();
        }
        else      // child forms are opened
        {