private void CallBackForUserDetails(User user)
 {
     Device.BeginInvokeOnMainThread(() =>
     {
         var record = AvailableDevices.Where(a => a.IPAddress == user.IPAddress);
         if (record.Any())
         {
             AvailableDevices.Remove(record.First());
         }
         AvailableDevices.Add(new User()
         {
             IPAddress = user.IPAddress, Name = user.Name
         });
     });
 }