WHAT IS this.Dispatcher.BeginInvoke(() => AND ITS USE???

Question

HAI IAM GETTING ERROR in my code i cant fix can you help me? am trying to develope a widows phone 8.1 chat app and am new to this

 

 

ERROR IS IN  this.Dispatcher.BeginInvoke(() =>  SECTION..

widows.ui.core.core dispatcher does not contain adefinition for BeginInvoke and no extension methode BeginInvoke accepting a first argument of  type windows.ui.core.core dispatcher could not find(are you missing a using directives or assembly refference?)

 

 

 

 

using System;

using System.Collections.Generic;

using System.IO;

using System.Linq;

using System.Runtime.InteropServices.WindowsRuntime;

using Windows.Foundation;

using Windows.Foundation.Collections;

using Windows.UI.Xaml;

using Windows.UI.Xaml.Controls;

using Windows.UI.Xaml.Controls.Primitives;

using Windows.UI.Xaml.Data;

using Windows.UI.Xaml.Input;

using Windows.UI.Xaml.Media;

using Windows.UI.Xaml.Navigation;

using System.Net.XMPP;

using System.Threading;

// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=391641

namespace test_demo

{

public sealed partial class MainPage : Page

{

public XMPPClient ObjXmppClient { get; set; }

public XMPPConnection ObjXmppCon { get; set; }

public string username;

public string password;

public readonly string server = "taurus";

private Boolean IsXmppSuccess { get; set; }

public MainPage()

{

this.InitializeComponent();

this.NavigationCacheMode = NavigationCacheMode.Required;

}

void ObjXmppCon_OnAsyncConnectFinished(xmedianet.socketserver.SocketClient client, bool bSuccess, string strErrors)

{

IsXmppSuccess = client.Connected;

}

void xMPPClient_OnStateChanged(object sender, EventArgs e)

{

switch (ObjXmppClient.XMPPState)

{

case XMPPState.Ready:

if (IsXmppSuccess)

{

this.Dispatcher.BeginInvoke(() =>  //ERROR HERE-

widows.ui.core.core dispatcher does not contain adefinition for BeginInvoke and no extension methode BeginInvoke accepting a first argument of type windows.ui.core.core dispatcher could not find(are you missing a using directives or assembly refference?)

{

Frame.Navigate(typeof(Logedin))

;

});

}

else

{

this.Dispatcher.BeginInvoke(() =>

{

MessageBox.Show("Check server name/IpAddress");

return;

});

}

break;

case XMPPState.AuthenticationFailed: this.Dispatcher.BeginInvoke(() =>

{

MessageBox.Show("Enter valid username and password");

//NavigationService.Navigate((new Uri("/Output.xaml?key=wrong", UriKind.Relative)));

return;

}); break;

}

}

protected override void OnNavigatedTo(NavigationEventArgs e)

{

}

}

}