title: Mock data not showing when bound to ICollectionView
body: <p>If I bound my <code>ListBox</code> to ViewModels <code>ObservableCollection</code> or XAML resourced <code>CollectionViewSource</code>, the mock data shows while in design. </p>
  
  <p>Sometimes <code>CollectionViewSource</code> stops showing this data because of some XAML changes, but after rebuilding the code it fills controls back with fake data again.</p>
  
  <p>Grouping, sorting and filtering in my case are controlled in ViewModel (and retried from database) so I decided to move over to <code>ICollectionView</code> property based in ViewModel. Unfortunately Views are no longer getting mock data at all. </p>
  
  <p>Here is simple example of my approaches:</p>
  
  <pre><code>&lt;Window x:Class="Test.MainWindow"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
          xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
          xmlns:local="clr-namespace:Test"
  
          mc:Ignorable="d"
          d:DataContext="{d:DesignInstance local:MainWindowViewModel }"
  
          Title="MainWindow" Height="100" Width="525"
      &gt;
  
      &lt;Window.Resources&gt;
  
          &lt;CollectionViewSource x:Key="ItemsCollectionViewSource" Source="{Binding ItemsObservableCollection}"/&gt;
  
      &lt;/Window.Resources&gt;
  
      &lt;UniformGrid Columns="6"&gt;
  
          &lt;ListBox ItemsSource="{Binding ItemsObservableCollection}" Background="WhiteSmoke" /&gt;
  
          &lt;ListBox ItemsSource="{Binding Source={StaticResource ItemsCollectionViewSource}}" Background="LightYellow" /&gt;
  
          &lt;ListBox ItemsSource="{Binding ItemsICollectionView}" Background="WhiteSmoke" /&gt;
  
          &lt;ListBox ItemsSource="{Binding ItemsCollectionView}" Background="LightYellow" /&gt;
  
          &lt;ListBox ItemsSource="{Binding ItemsListCollectionView}" Background="WhiteSmoke" /&gt;
  
          &lt;ListBox ItemsSource="{Binding ItemsBackCollectionViewSource}" Background="LightYellow" /&gt;
  
      &lt;/UniformGrid&gt;
  
  &lt;/Window&gt;
  </code></pre>
  
  <p>code behind:</p>
  
  <pre><code>namespace Test
  {
      public partial class MainWindow
      {
          public MainWindow()
          {
              DataContext = new MainWindowViewModel();
  
              InitializeComponent();
          }
      }
  }
  </code></pre>
  
  <p>and ViewModel:</p>
  
  <pre><code>using System.Collections.ObjectModel;
  using System.ComponentModel;
  using System.Windows.Data;
  
  namespace Test
  {
      public class MainWindowViewModel
      {
          public ICollectionView ItemsICollectionView { get; set; }
  
          public CollectionView ItemsCollectionView { get; set; }
  
          public ListCollectionView ItemsListCollectionView { get; set; }
  
          public ObservableCollection&lt;string&gt; ItemsObservableCollection { get; set; }
  
          public CollectionViewSource ItemsBackCollectionViewSource { get; set; }
  
          public MainWindowViewModel()
          {
              ItemsObservableCollection = new ObservableCollection&lt;string&gt; {"a", "b", "c"};
  
              ItemsICollectionView = CollectionViewSource.GetDefaultView(ItemsObservableCollection);
  
              ItemsCollectionView = CollectionViewSource.GetDefaultView(ItemsObservableCollection) as CollectionView;
  
              ItemsListCollectionView = CollectionViewSource.GetDefaultView(ItemsObservableCollection) as ListCollectionView;
  
              ItemsBackCollectionViewSource = new CollectionViewSource {Source = ItemsObservableCollection};
          }
      }
  }
  </code></pre>
  
  <p>None of methods I have tried in order to move CollectionViewSource to ViewModel allows me to see mock data:</p>
  
  <p><a href="https://i.stack.imgur.com/hCAlP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hCAlP.png" alt="enter image description here"></a></p>
  
  <p>I did some debug comparison on those controls, but they are set pretty same in a run time. I'm not aware of ability to debug at design time.</p>
  
  <p>Is there something I'm missing, or it has to be that way? 
  Thanks</p>