title: Listview populated with empty entities
body: <p>So I have an <code>ObservableCollection</code> of <code>IDevice</code> which contains a collection bluetooth devices in the periphery. </p>
  
  <pre><code>public partial class MainPage : ContentPage
  {
  
      public ObservableCollection&lt;IDevice&gt; Devices { get; set; }
  
      public MainPage()
      {
          Devices = new ObservableCollection&lt;IDevice&gt;();
          Padding = new Thickness(0, 20, 0, 0);
          var listView = new ListView();
          listView.ItemsSource = Devices;
          Content = listView;
          Refreshcmd();
      }
  
      public void Refreshcmd()
      {
          var adapter = CrossBluetoothLE.Current.Adapter;
          adapter.DeviceDiscovered += (s, a) =&gt; Devices.Add(a.Device);
          adapter.StartScanningForDevicesAsync();
      }
  }   
  </code></pre>
  
  <p>My problem is, that the listview is populated with empty entities as well, besides the actual Bluetooth devices, which results in a very long list with actual devices on every 5th line or so. </p>
  
  <p>I suspect that the error occurs upon adding data to <code>Devices</code>. I believe A fix would be to alter the lambda expression with a condition, so that device != empty ish. Also, it could maybe be possible to go the other way around, and somehow tell the listview that it shouldn't show "empty" data. </p>
  
  <p>I'm just unsure how i would go about doing so. </p>