WPF Filtering a CollectionViewSource

I have a WPF project that draws data from a dataset. In one particular view I have a grid and I want to show a filtered version of the data

I've read that I cant Filter a BindingListView but this is a CollectionViewSource

My code is this:-

Private Sub UserControl_Loaded_1(sender As Object, e As RoutedEventArgs) Handles MyBase.Loaded

 Dim _ds As CantileverDataSet
 Dim _carcasseTableAdapter As CantileverDataSetTableAdapters.MaterialsTableAdapter
 Dim _carcasseViewSource As CollectionViewSource

 _ds = CType(Me.FindResource("CantileverDataSet"), CantileverDataSet)

 _carcasseTableAdapter = New CantileverDataSetTableAdapters.MaterialsTableAdapter
 _carcasseTableAdapter.Fill(_ds.Materials)
 _carcasseViewSource = CType(Me.FindResource("MaterialsViewSource"), CollectionViewSource)

 AddHandler _carcasseViewSource.Filter, AddressOf CarcasseFilter
End Sub

Private Sub CarcasseFilter(ByVal sender As System.Object, ByVal e As FilterEventArgs)
    'Accept everything for now

    e.Accepted = True
End Sub

The error I get is

'System.Windows.Data.BindingListCollectionView' view does not support filtering.

If I do _carcasseViewSource.GetType I get CollectionViewSource If I do _carcasseViewSource.View.GetType I get BindingListCollectionView

It's as if it is treating my _carcasseViewSource as a BindingListCollectionView regardless

Here is the XAML of the grid just in case

    <Grid x:Name="CarcasseGrid" DataContext="{StaticResource MaterialsViewSource}" >
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <Label Content="Material Code:" Grid.Column="0" Grid.Row="0"/>
        <TextBox x:Name="MaterialCodeTextBox" Grid.Column="1" Grid.Row="0" Text="{Binding MaterialCode, Mode=TwoWay, NotifyOnValidationError=true, ValidatesOnExceptions=true}"/>
        <Label Content="Name:" Grid.Column="0" Grid.Row="1"/>
        <TextBox x:Name="NameTextBox" Grid.Column="1" Grid.Row="1" Text="{Binding Name, Mode=TwoWay, NotifyOnValidationError=true, ValidatesOnExceptions=true}"/>
    </Grid>

Any thoughts would be greatly appreciated