以MDI格式多次防止相同的子窗口

Question

我正在使用c＃桌面应用程序，在MDI窗体中，当您单击菜单时会打开相同的子窗口，而该窗口的第一个实例存在。 如何以MDI格式阻止子窗口的这些多个实例？

Answer 1

您可以检查表单是否已经打开：

  Form instance = null;

  // Looking for MyForm among all opened forms 
  foreach (Form form in Application.OpenForms) 
    if (form is MyForm) {
      instance = form;

      break; 
    }

  if (Object.ReferenceEquals(null, instance)) {
    // No opened form, lets create it and show up:
    instance = new MyForm();
    instance.Show();
    ...
  }
  else {
    // MyForm has been already opened

    // Lets bring it to front, focus, restore it sizes (if minimized)
    if (instance.WindowState == FormWindowState.Minimized)
      instance.WindowState = FormWindowState.Normal; 

    instance.BringToFront();

    if (instance.CanFocus) 
      instance.Focus();
    ...
  }

Answer 2

也许这可以帮到你：

public static bool formOpened = false;   // it is global boolean
Form2 instance;

当您打开表单时：

if(formOpened == false)
{
   instance = new Form2();
   instance.Show();
   formOpened = true;
}
else
{
    instance.Focus();
}

还有一件事是在关闭Form2之后，你应该将formOpened的值设置为false;