wpf 热键问题

以下是代码，运行起来热键没用，求解决的方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Runtime.InteropServices;
using System.Windows.Interop;

namespace WpfApplication2
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        [DllImport("user32.dll")]
        public static extern bool RegisterHotKey(IntPtr hWnd, int id, uint control,Key key);
        [DllImport("user32.dll")]
        public static extern bool UnregisterHotKey(IntPtr hWnd, int id);

        public static int WM_HOTKEY = 0x0312;
        public Window1()
        {
            InitializeComponent();
            this.Closed += new EventHandler(Window1_Closed);
        }
        void Window1_Closed(object sender, EventArgs e)
        {
            IntPtr hWnd = new WindowInteropHelper(this).Handle;
            UnregisterHotKey(hWnd, 123);
        }
        protected override void OnSourceInitialized(EventArgs e)
        {
            base.OnSourceInitialized(e);
            IntPtr hWnd = new WindowInteropHelper(this).Handle;
            RegisterHotKey(hWnd, 123, 0, System.Windows.Input.Key.Escape);// System.Windows.Forms.Keys.EscapeKey.Escape

            HwndSource source = PresentationSource.FromVisual(this) as HwndSource;
            source.AddHook(WndProc);
        }

        private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            if (msg == WM_HOTKEY)
            {
                MessageBox.Show("OK");
                if (wParam.ToInt32() == 123)
                {
                    MessageBox.Show("OK");
                    handled = true;
                }
            }
            return IntPtr.Zero;
        }
    }
}

补充：.NET技术 ,  C#