WPF中嵌入WinForm做的远程桌面的焦点问题

Question

我原来做了一个基于WinForm的远程桌面，现在想把它嵌入到WPF中。

现在碰到一个问题，我可以打开远程桌面，且可以操作，但是，当切到另外一个程序后在回到这个远程桌面时，就失去焦点，无法操作了，必须按一下Tab键才可以使用。请问如何操作可以使得鼠标进入远程桌面时就自动获得焦点？

PS：在第一失去焦点，按了Tab后，再怎么切入切出都可以获得焦点，why？

远程桌面的cs文件（Form）

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using AxMSTSCLib;
using System.Threading;

namespace RemoteDesktop
{
    public partial class RDP : Form
    {
        public AutoResetEvent windowsEvent = new AutoResetEvent(false);
        private AxMSTSCLib.AxMsRdpClient2 rdpClient;
        public RDP(string ip,string usrname, string passwd)
        {
            InitializeComponent();
            this.Text = ip + " by " + usrname;
            this.Hide();
            this.FormBorderStyle = FormBorderStyle.None;
            this.WindowState = FormWindowState.Maximized;
            try
            {
                rdpClient = new AxMSTSCLib.AxMsRdpClient2();

                rdpClient.Dock = DockStyle.Fill;
                rdpClient.Width = Screen.PrimaryScreen.Bounds.Width;
                rdpClient.Height = Screen.PrimaryScreen.Bounds.Height;
                rdpClient.BeginInit();
                this.Controls.Add(rdpClient);
                rdpClient.EndInit();
                rdpClient.OnDisconnected += new AxMSTSCLib.IMsTscAxEvents_OnDisconnectedEventHandler(rdpClient_OnDisconnected);
                rdpClient.OnConfirmClose += new AxMSTSCLib.IMsTscAxEvents_OnConfirmCloseEventHandler(rdpClient_OnConfirmClose);
                rdpClient.Server = ip;
                rdpClient.UserName = usrname;
                rdpClient.AdvancedSettings2.RDPPort = 3389;
                rdpClient.AdvancedSettings2.ClearTextPassword = passwd;
                rdpClient.ColorDepth = 16;
                rdpClient.FullScreen = false ;

                rdpClient.Connect();
            }
            catch (Exception ex)
            { MessageBox.Show(ex.Message); }
        }

        void rdpClient_OnConfirmClose(object sender, IMsTscAxEvents_OnConfirmCloseEvent e)
        {
            this.Close();
        }


        void rdpClient_OnDisconnected(object sender, AxMSTSCLib.IMsTscAxEvents_OnDisconnectedEvent e)
        {
            MessageBox.Show("发生错误需要关闭，错误代码：" + e.discReason);
            this.Close();
        }
    }
}

wpf的框

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.Shapes;
using RemoteDesktop;

namespace remote_desktop_wfp
{
    /// <summary>
    /// Window2.xaml 的交互逻辑
    /// </summary>
    public partial class Window2 : Window
    {
        public Window2()
        {
            InitializeComponent();
            ShowRemoteDesktop(new RemoteDesktopArgs("172.16.60.228", "123456", "Administrator"));
        }

        public class RemoteDesktopArgs
        {
            public string ip { get; set; }
            public string password { get; set; }
            public string user { get; set; }
            public RemoteDesktopArgs(string i, string p, string u) { ip = i; password = p; user = u; }
        }

        void ShowRemoteDesktop(RemoteDesktopArgs rdpargs)
        {

            System.Windows.Forms.Integration.WindowsFormsHost host =
            new System.Windows.Forms.Integration.WindowsFormsHost();

            RDP rdp = new RDP(rdpargs.ip, rdpargs.user, rdpargs.password);
            rdp.TopLevel = false;

            host.Child = rdp;
            host.MouseEnter += new MouseEventHandler(host_MouseEnter);
            host.MouseMove += new MouseEventHandler(host_MouseMove);
            host.Focusable = false;

            grid.Children.Add(host);

        }

        void host_MouseMove(object sender, MouseEventArgs e)
        {
            RDP rdp = (sender as System.Windows.Forms.Integration.WindowsFormsHost).Child as RDP;
            rdp.Focus();
        }

        void host_MouseEnter(object sender, MouseEventArgs e)
        {
            RDP rdp = (sender as System.Windows.Forms.Integration.WindowsFormsHost).Child as RDP;
            rdp.Focus();

        }
    }
}