Wait for MDI child to close, similar to ShowDialog()

Question

I've got a MDI-Application in which I'd like to use modal dialogs...yes, I know that this is a little against the principles if MDI...anyway, my main window is more of a 'workspace' then anything else.

Back to topic, how can I wait for an MDI-Child to close? Some example code:

  public void DoSomething() {
    String searchterm = this.TextBox1.Text;
    MyItem result = MySearchForm.GetItem(searchterm);

    if(MyItem != MyItem.Empty) {
        // do something
    }
  }

MySearchForm is a MDI-Child of the main window, so I can't use ShowDialog(), but I'd still like to use a blocking method to wait for the window to close and return the result. I thought about calling it on another thread and wait for that one to exit, but that also doesn't work with MDI.

Does somebody have an idea?

Answer 1

Simply move focus back to the MDI child if it loses it. Hook the LostFocus event in the MDI child window and use this.SetFocus();

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.enter.aspx

Answer 2

Overload the FormClosing event of the main window:

void MyForm_FormClosing(object sender, FormClosingEventArgs e)
{
    if (e.CloseReason == CloseReason.UserClosing)
    {
        // User clicked the close button.
        // Cancel if dialogs are open.
        if (dialogsOpen)
        {
            e.Cancel = true;
        }
    }
}

Answer 3

Try disabling the main form, then re-enabling it when the child form closes. It would be a bit like this:

  public void DoSomething() 
  {
    searchForm.Show();
    searchForm.SearchTerm = this.TextBox1.Text;
    searchForm.FormClosing += new FormClosingEventHandler(searchForm_FormClosing);

    this.Enabled = false
  }

  void searchForm_FormClosing(object sender, FormClosingEventArgs e)
  {
    this.Enabled = true;

    // Get result from search form here
    MyItem result = searchForm.GetItem();
    if(MyItem != MyItem.Empty) // do something
  }

Answer 4

Using dialogs in an MDI application is quite normal, it doesn't violate MDI conventions. Just don't make it a MDI child window. That's bad because you cannot make it modal. And if you make it non-modal then confuzzling things happen when the user minimizes the window.

Just use the ShowDialog(owner) or Show(owner) method (respectively modal and non-modal) and pass the MDI parent as the owner. The dialog will always be on top of the child windows. You typically do want StartPosition = Manual and set Location so you can be sure it starts up at an appropriate position within the parent frame.