title: Listview not populating after page navigation in Xamarin
body: <p>I have <code>ListView</code> defined in xaml as below:</p>
  
  <pre><code>&lt;ListView x:Name="Iv" ItemSelected="Iv_ItemSelected" ItemsSource="{Binding deviceListEx}"&gt;
      &lt;ListView.ItemTemplate&gt;
          &lt;DataTemplate&gt;
              &lt;ViewCell&gt;
                  &lt;StackLayout&gt;
                      &lt;Label Text="{Binding .}" /&gt;
                  &lt;/StackLayout&gt;
              &lt;/ViewCell&gt;
          &lt;/DataTemplate&gt;
      &lt;/ListView.ItemTemplate&gt;
  &lt;/ListView&gt;
  </code></pre>
  
  <p>This does work in first page load, however in iOS platform when I navigate to another page then back to the listview page by clicking back button, the page is blank, means listview is not populating.</p>
  
  <p>Application is in c# and working fine in android.</p>
  
  <p>Have anyone faced such issue or similar issue? Do let me know how can I solve this.</p>
  
  <p>This is the code behind. The listview item source is the result of a bluetooth scan and it is a <code>ObservableCollection&lt;string&gt;</code>.</p>
  
  <pre><code>deviceList.Clear();
  deviceListEx.Clear();
  var scanner = CrossBleAdapter.Current.ScanWhenAdapterReady().
  Subscribe(ScanResult =&gt;
  {     
     if (ScanResult.Device.Name != null)
         {
            deviceList.Add(ScanResult.Device);                             
            deviceListEx.Add(ScanResult.Device.Name.ToString());
            // unique bluetooth devices with name to listview
            Iv.ItemsSource = deviceListEx.Distinct();
             }          
  
      });
  </code></pre>