How to pick folder with OpenFileDialog?

OpenFileDialog allows selection of files, and FolderBrowserDialog allows selection of folders. For various legitimate reasons, I prefer to use OpenFileDialog for folders instead. The question is, how?

Overriding FileDialog.HookProc to obtain the dialog handle to change the dialog behavior is my first attempt, but it is immediately obvious that OpenFileDialog is sealed and cannot be inherited, and I don't feel like reimplementing everything with GetOpenFileName. So an alternative way to get the dialog handle is to cook up a dummy window (as in FileDialog > DummyOwner > RealOwner) and watch for WM_ACTIVATE in the overriden WndProc. As always, be extra careful when playing with window activation.

Now, with the dialog handle, and later the child notification dialog handle, I can do pretty much what I want. I can hide and rename various controls on the dialog, handle BN_CLICKED to accept folder, and more.

A few gotchas include having to do manual marshaling using COM task memory, but no big deal.

Next up is the Vista version.