How do I determine if a WPF window is modal?

From http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/c95f1acb-5dee-4670-b779-b07b06afafff/

"System.Windows.Interop.ComponentDispatcher.IsThreadModal can tell you if the calling thread is currently running a modal hwnd."

Okay, since my last idea got voted down, I proved it. this works - and I tested it in a new WPF application, so I know it works:

In my main Window's (Window1) Loaded event, I did:

Dim frm As New Window2
frm.ShowDialog()

In my Window2 I shadowed the ShowDialog() method

Private _IsModal As Boolean = False 'This will be changed in the IsModal method

Public Property IsModal() As Boolean
  Get
    Return _IsModal
  End Get
  Set(ByVal value As Boolean)
    _IsModal = value
  End Set
End Property

Public Shadows Sub ShowDialog()
  IsModal = True
  MyBase.ShowDialog()
End Sub

In my Loaded event, I then fired off a message box to make sure that the IsModal property got changed from False to True and it gives me True, so I know IsModal was set. MyBase.ShowDialog() then forces the base class to be loaded as Modal. Shadows allows us to override the default behaviour even though the ShowDialog() method wasn't declared as overridable.

While it doesn't "self determine" it doesn't require you to pass in any boolean value from outside, and doesn't require you to set the IsModal from outside, it sets it inside itself, it's accessible from outside if you so chose to use it that way. It sets the value only if it us loaded using the ShowDialog() method and not if you use the Show() method. I doubt you'll find a much simpler method of doing this.

There's a private field _showingAsDialog whenever a WPF Window is a modal dialog. You could get that value via reflection and incorporate it in an extension method:

public static bool IsModal(this Window window)
{
    return (bool)typeof(Window).GetField("_showingAsDialog", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(window);
}

The value is set to true when the window is shown as modal (ShowDialog) and set to false once the window closes.