WPF TextBox not accepting Input when in ElementHost in Window Forms

I finally figured it out after 2 days of head scatching...

The MFC Dialog window was taking the WM_CHAR messages and preventing the control from handling the input. So in order to prevent this, I hook the HwndSource and whenever I receive the WM_GETDLGCODE message I respond back with the types of input to accept, and then mark the event as handled.

I created my own TextBox in order to prevent having to fix every textbox (see Below):

    /// <summary>    /// Interop Enabled TextBox : This TextBox will properly handle WM_GETDLGCODE Messages allowing Key Input    /// </summary>    class IOTextBox : TextBox    {        private const UInt32 DLGC_WANTARROWS = 0x0001;        private const UInt32 DLGC_WANTTAB = 0x0002;        private const UInt32 DLGC_WANTALLKEYS = 0x0004;        private const UInt32 DLGC_HASSETSEL = 0x0008;        private const UInt32 DLGC_WANTCHARS = 0x0080;        private const UInt32 WM_GETDLGCODE = 0x0087;        public IOTextBox() : base()        {            Loaded += delegate                          {                              HwndSource s = HwndSource.FromVisual(this) as HwndSource;                              if (s != null)                                  s.AddHook(new HwndSourceHook(ChildHwndSourceHook));                          };        }        IntPtr ChildHwndSourceHook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)        {            if (msg == WM_GETDLGCODE)            {                handled = true;                return new IntPtr(DLGC_WANTCHARS | DLGC_WANTARROWS | DLGC_HASSETSEL);            }            return IntPtr.Zero;        }    }

Check out my own question about this very same thing. in the end though, all you need is something like this:

Window window1 = new Window();ElementHost.EnableModelessKeyboardInterop(window1);window1.Show();

Why is my WPF textbox "kinda" readonly?

I have a similar issue with a wxWidgets parent window and embedded WPF TextBox controls. I found that although attaching ChildHwndSourceHook does solve the problem of not receiving keyboard input, I ended up with occasional duplicate space characters. It seems the WM_KEYDOWN message handles the space characters reliably, but a duplicate WM_CHAR message is also received for some of the spaces. To solve this I added the following clause to the body of the ChildHwndSourceHook function, which simply ignores the WM_CHAR space character:

        const UInt32 WM_CHAR = 0x0102;        if (msg == WM_CHAR)        {            // avoid duplicated spaces when parent window is a native window            if (wParam.ToInt32() == 32)                handled = true;        }