How to set focus on richeditbox in metro style app?
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I have the following code:  

 

     private async void SendMsg_Click(object sender, RoutedEventArgs e)
    {
     RichEditBox.Document.SetText(TextSetOptions.None, "");
     await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
        {
           if(RichEditBox!=null)
           SendBox.Focus(Windows.UI.Xaml.FocusState.Keyboard);
        });
     }

but when clicked,the RichEditBox didnot got focus.What's wrong with my code? thanks