I'm getting an annoying binding error that's basically my last roadblock with this control:

> 
> *System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=SearchResults; DataItem=null; target element is 'CollectionViewSource' (HashCode=6017800); target property is 'Source' (type 'Object')*
> 
> 
> 

Here's the `TabControl`'s markup:

```
<TabControl ItemsSource="{Binding Tabs}" SelectedItem="{Binding SelectedTab}">

    <TabControl.ItemTemplate>
        <!-- tab header template works as intended -->
    </TabControl.ItemTemplate>

    <TabControl.ContentTemplate>

        <DataTemplate DataType="controls:SearchResultsViewModel">

            <DataTemplate.Resources>
                <CollectionViewSource x:Key="GroupedSearchResults" 
                                      Source="{Binding SearchResults}">
                    <CollectionViewSource.SortDescriptions>
                        <!-- sort descriptions -->
                    </CollectionViewSource.SortDescriptions>
                    <CollectionViewSource.GroupDescriptions>
                        <!-- group descriptions -->
                    </CollectionViewSource.GroupDescriptions>
                </CollectionViewSource>
            </DataTemplate.Resources>

            <controls:GroupingGrid ShowGroupingItemCount="True"
                                   ItemsSource="{Binding Source={StaticResource GroupedSearchResults}}"
                                   SelectedItem="{Binding SelectedItem}">
                <DataGrid.Columns>
                    <!-- column definitions -->
                </DataGrid.Columns>
            </controls:GroupingGrid>

        </DataTemplate>
    </TabControl.ContentTemplate>
</TabControl>

```

The designer gives me no squiggly lines anywhere, which seems to indicate everything is ok; I only get the binding error at run-time, however the ViewModels (serach results) populate exactly as expected... they just don't bind into the `CollectionViewSource` for some reason.

What am I doing wrong?