WinForms - detect if any dialog windows are open

I have a timer in the main application form.

The timer displays a nag screen every N seconds.

But I'd like to a开发者_Python百科void showing the nag screen if any modal dialog windows are open. Otherwise overlapping will occur.

I can use Application.OpenForms, but this doesn't count dialogs such as OpenFileDialog.

How to detect if any child dialogs are currently shown?

Consider using these Win32 apis:

GetForegroundWindow();
GetAncestor(foregroundWindow, GA_ROOTOWNER);
GetWindowThreadProcessId(foregroundWindow, out activeProcessId)