title: Item not changing group in a grouped listview
body: <p>I have a listView in which I show a collection of Vehicles which are grouped by their MaintenanceState. If the MaintenanceState of the Vehicle updates I expect it to change group. The collection itself is correctly updated, however the view does not update accordingly. Below is some of my code, maybe someone can help me getting this to work.</p>
  
  <p>This is my CollectionViewSource managing my groupings</p>
  
  <pre><code>&lt;CollectionViewSource x:Key="GroupedVehicles" IsLiveGroupingRequested="True" Source="{Binding ItemCollection}"&gt;
     &lt;CollectionViewSource.GroupDescriptions&gt;
        &lt;PropertyGroupDescription PropertyName="MaintenanceState" /&gt;
     &lt;/CollectionViewSource.GroupDescriptions&gt;
  &lt;/CollectionViewSource&gt;
  </code></pre>
  
  <p>Here is my ListView</p>
  
  <pre><code>    &lt;ListView ItemContainerStyle="{DynamicResource VehicleItemContainerStyle}"
                ItemsSource="{Binding Source={StaticResource GroupedVehicles}}"
                SelectedItem="{Binding SelectedItem}"
                SelectionMode="Single"
                Style="{DynamicResource VehiclesListViewStyle}"&gt;
         &lt;ListView.GroupStyle&gt;
            &lt;GroupStyle&gt;
               &lt;GroupStyle.ContainerStyle&gt;
                  &lt;Style TargetType="{x:Type GroupItem}"&gt;
                     &lt;Setter Property="Template"&gt;
                        &lt;Setter.Value&gt;
                           &lt;ControlTemplate TargetType="{x:Type GroupItem}"&gt;
                              &lt;StackPanel&gt;
                                 &lt;Expander Header="{Binding Path=Name}"
                                           IsExpanded="True"
                                           Style="{DynamicResource VehicleListSectionExpanderStyle}"&gt;
                                    &lt;ItemsPresenter /&gt;
                                 &lt;/Expander&gt;
                              &lt;/StackPanel&gt;
                           &lt;/ControlTemplate&gt;
                         &lt;/Setter.Value&gt;
                      &lt;/Setter&gt;
                   &lt;/Style&gt;
                &lt;/GroupStyle.ContainerStyle&gt;
             &lt;/GroupStyle&gt;
          &lt;/ListView.GroupStyle&gt;
          &lt;ListView.ItemTemplate&gt;
             &lt;DataTemplate&gt;
                &lt;TextBlock Text="{Binding Number}" /&gt;
             &lt;/DataTemplate&gt;
          &lt;/ListView.ItemTemplate&gt;
  &lt;/ListView&gt;
  </code></pre>
  
  <p>This is what I do on my ViewModel</p>
  
  <pre><code>Vehicle updatedVehicle = new Vehicle(vehicleNumber, MaintenanceStateEnum.Running);
  ItemCollection[index] = updatedVehicle;
  </code></pre>
  
  <p>The ItemCollection is of type <code>ObservableCollection&lt;Vehicle&gt;</code> and I make sure to only add, remove or replace Vehicles.
  The MaintenanceStateEnum has the following values: InMaintenance, MarkedForMaintenance and Running.</p>
  
  <p>This is what my Vehicle looks like</p>
  
  <pre><code>public class Vehicle
  {
      public Vehicle(int number, MaintenanceStateEnum state) {}
      public int Number { get; private set; }
      public MaintenanceStateEnum MaintenanceState { get; private set; }
  }
  </code></pre>
  
  <p>So my problem:</p>
  
  <p>If I have  Vehicle(3, MaintenanceStateEnum.MarkedForMaintenace) and it is updated to Vehicle(3, MaintenanceStateEnum.InMaintenance) it does not change from the grouping MarkedForMaintenance to the grouping InMaintenance. 
  Interesting is that it does get removed from the MarkedForMaintenance grouping (the view even leaves a space as if the object is still there).</p>
  
  <p>Does anyone know how I can fix my problem?</p>