窗体句柄问题

        private bool haveMainWindow = false;
        private IntPtr mainWindowHandle = IntPtr.Zero;
        private int processId = 0; private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            ///初始化录音句柄等
            processId = Process.GetCurrentProcess().Id;
            BaseData.hwnd = GetMainWindowHandle(processId);            
        } private IntPtr GetMainWindowHandle(int processId)
        {
            if (!haveMainWindow)
            {
                this.mainWindowHandle = IntPtr.Zero;
                this.processId = processId;
                User32API.EnumThreadWindowsCallback callback = new User32API.EnumThreadWindowsCallback(this.EnumWindowsCallback);
                User32API.EnumWindows(callback, IntPtr.Zero);
                GC.KeepAlive(callback);                haveMainWindow = true;
            }
            return this.mainWindowHandle;
        }        private bool EnumWindowsCallback(IntPtr handle, IntPtr extraParameter)
        {
            int num;
            User32API.GetWindowThreadProcessId(new HandleRef(this, handle), out num);
            if ((num == this.processId) && this.IsMainWindow(handle))
            {
                this.mainWindowHandle = handle;
                return false;
            }
            return true;
        }        private bool IsMainWindow(IntPtr handle)
        {
            return (!(User32API.GetWindow(new HandleRef(this, handle), 4) != IntPtr.Zero) && User32API.IsWindowVisible(new HandleRef(this, handle)));
        }