Dockfill not working in mstsc activeX control

Question

I am trying to create a rdp in WPF. I used the AxMSTSCLib library to create a rdp client in my wpf application. I planned to create a usercontrol that hosts the rdp.I achieved it with the following code. But i get the grey area of the windows host visible. I need to fill the rdp client for the size of the windows host.

 public partial class RDPUserControl : UserControl
    {
        internal RDPActiveXControl _rdp;
        internal string Servername { get; set; }
        internal string Username { get; set; }
        internal string Password { get; set; }
        internal TabItem TabItem { get; set; }
        public RDPUserControl()
        {
            InitializeComponent();
        }
 
        private void InitData()
        {
            _rdp = new RDPActiveXControl();
            ((System.ComponentModel.ISupportInitialize)(_rdp)).BeginInit();
            _rdp.Name = "rdp";
            _rdp.Enabled = true;
            wfHost.Child = _rdp;
            ((System.ComponentModel.ISupportInitialize)(_rdp)).EndInit();
        }

        internal void Connect()
        {
            _rdp.Server = Servername;
            _rdp.UserName = Username;
            _rdp.AdvancedSettings7.ClearTextPassword = Password;
            _rdp.ColorDepth = 24;
            _rdp.AdvancedSettings7.SmartSizing = true;
            _rdp.AdvancedSettings7.AuthenticationLevel = 2;
            _rdp.AdvancedSettings7.EnableCredSspSupport = true;
            _rdp.Width = Convert.ToInt32(this.ActualWidth);
            _rdp.Height = Convert.ToInt32(this.ActualHeight);
            _rdp.DesktopWidth = Convert.ToInt32(this.ActualWidth);
            _rdp.DesktopHeight = Convert.ToInt32(this.ActualHeight);
            _rdp.OnDisconnected += _rdp_OnDisconnected;
            try
            {
                _rdp.Connect();
            }
            catch(Exception e)
            {
                MessageBox.Show("Connection Failed: "+e.Message);
            }
        }

        private void _rdp_OnDisconnected(object sender, AxMSTSCLib.IMsTscAxEvents_OnDisconnectedEvent e)
        {
            MainWindow window = Application.Current.MainWindow as MainWindow;
            Page page = window._mainFrame.Content as Page;
            ConnectionsPage connectionPage = page as ConnectionsPage;
            connectionPage.CloseTab(TabItem);
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            InitData();
            Connect();
        }

    public class RDPActiveXControl : AxMSTSCLib.AxMsRdpClient6NotSafeForScripting
    {
        public RDPActiveXControl() : base() { }

        protected override void WndProc(ref System.Windows.Forms.Message m)
        {
            // Fix for the missing focus issue on the rdp client component
            if (m.Msg == 0x0021) // WM_MOUSEACTIVATE
            {
                if (!this.ContainsFocus)
                {
                    this.Focus();
                }
            }

            base.WndProc(ref m);
        }

    }

How to make the RDP ActiveXControl for Full size of the windowsFormHost

I tried with

_rdp.Dock = System.Windows.Forms.DockStyle.Fill;

But it makes the app to disappear.Anyone know what is wrong with this?. Any working example will be helpful.