or
<telerik:GridViewComboBoxColumn Header="Units" ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}},Path=DataContext.UnitsOfMeasure}" DisplayMemberPath="Name" DataMemberBinding="{Binding UnitOfMeasureID}" SelectedValueMemberPath="Id"/>

<telerik:RadGridView x:Name="RadGridView1" Grid.Row="2" ItemsSource="{Binding ResultsViewModelList}" AutoGenerateColumns="False" custom:GridViewDataColumnsBehavior.BindableColumns="{Binding ColumnCollection}" SelectionMode="Extended" ScrollViewer.VerticalScrollBarVisibility="Visible" ScrollViewer.HorizontalScrollBarVisibility="Auto" ColumnWidth="150" GroupRenderMode="Flat" EnableColumnVirtualization="False" ClipboardCopyMode="All" > <telerik:RadGridView.RowDetailsTemplate> <DataTemplate > <vw:ResultView DataContext="{Binding}"/> </DataTemplate> </telerik:RadGridView.RowDetailsTemplate> </telerik:RadGridView><telerik:RadGridView Name="radGridView1" AutoGenerateColumns="True" ItemsSource="{Binding Path=ItemsList}" ColumnWidth="150" GroupRenderMode="Flat" EnableColumnVirtualization="False" EnableRowVirtualization="False" ClipboardCopyMode="All" SelectionMode="Multiple" SelectionUnit="FullRow"> </telerik:RadGridView>