/// <summary>
/// This pokes into a given a HwndSource and extracts the window class atom for its hwnd
/// </summary>
/// <param name="source"></param>
/// <returns></returns>
private ushort GetClassAtom(HwndSource source)
{
object hwndWrapper;
Type hwndWrapperType;
// Grab WindowsBase and extract HwndWrapper's type
Assembly windowsBase = Assembly.GetAssembly(typeof(DependencyObject)); // get WindowsBase
hwndWrapperType = windowsBase.GetType("MS.Win32.HwndWrapper");
// Get the HwndWrapper from the HwndSource
FieldInfo hwndWrapperField = source.GetType().GetField("_hwndWrapper",
BindingFlags.NonPublic | BindingFlags.Instance);
hwndWrapper = hwndWrapperField.GetValue(source);
// Extract the class atom from the hwndWrapper
FieldInfo atomField = hwndWrapperType.GetField("_classAtom",
BindingFlags.NonPublic | BindingFlags.Instance);
return((ushort)atomField.GetValue(hwndWrapper));
}