Subclassing WPF window to handle custom messages

wpf-window-message-hook.cs

using System;
using System.Windows;
using System.Windows.Interop;

static class SubclassWindow
{
	// Call this from the constructor of your main window. SourceInitialized event is raised long after the constructor.
	public static void initialize( Window wnd )
	{
		wnd.SourceInitialized += ( object sender, EventArgs e ) => sourceInitialized( wnd );
	}

	static void sourceInitialized( Window window )
	{
		IntPtr handle = ( new WindowInteropHelper( window ) ).Handle;
		HwndSource.FromHwnd( handle ).AddHook( new HwndSourceHook( windowProcHook ) );
	}

	static IntPtr windowProcHook( IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled )
	{
		// Call C++ DLL here. Set handled to true if that window message was handled by the C++ code.
		if( interop.handleWindowMessage( hwnd, msg, wParam, lParam ) )
			handled = true;
		return IntPtr.Zero;
	}
}