Wpf: how can I bind strongly typed dataset and collectionviewsource

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WPF

I have a strongly typed DataSet (DataSet.xsd) with table "Credits".

This is easy to use for read/write table "Credits" to *.xml file.
Binding to DataGrid and view data is no problem.

But for filtering and grouping a CollectionViewSource seems necessary.

But with CollectionViewSource I get only an empty column with 7 rows.

What I have tried:

<Window.Resources>
                 
       <ResourceDictionary>
          <CollectionViewSource x:Key="Credits" Source= "Credits" 
...
    </Window.Resources>
    <Window.DataContext>
        <ViewModel:MainViewModel/>
    </Window.DataContext>

    <Grid >
        <controls:DataGridEx x:Name="dataGridEx" 
                  ItemsSource="{Binding Source=Credits}"
                  CanUserAddRows="False">

...
      <GroupStyle>
      <GroupStyle.ContainerStyle>
...
            <Expander.Content>
                 <ItemsPresenter DataContext="{DynamicResource Credits}" />
            </Expander.Content>

What is wrong there and how can I show my data with CollectionViewSource?