What technique does Snoop uses to inspect a WPF application

Question

Snoop, the spy utility, uses some powerful technique (probably some sort of reflection) to inspect a running WPF application. Most interesting is the fact, that Snnop is able to

Answer 1

The answer above doesn't work for me. It seems a bit vague. I expanded on accepted answer a little with this code:

    var allProcesses = Process.GetProcesses();
    var filteredProcess = allProcesses.Where(p => p.ProcessName.Contains(ProcessSearchText)).First();
    var windowHandle = filteredProcess.MainWindowHandle;
    var hwndSource = HwndSource.FromHwnd(windowHandle);

This answer seems more complete and will work for others if the accepted answer works for anyone. However, this the last line of this code returns null for me.