Binding GridComboBoxColumn CellTemplate to ItemsSource

Hello together,

I don't get my Subject working, can sb helpf me with the following code?

<syncfusion:GridComboBoxColumn x:Name="Angebot_KundeColumn" MappingName="Angebot_Kunde" HeaderText="Kunde Nachname" SelectedValuePath="Kunde_ID" ItemsSource="{StaticResource KundenView}" >
                    <syncfusion:GridComboBoxColumn.CellTemplate>
                        <DataTemplate>
                            <StackPanel Orientation="Horizontal">
                                <Label Content="{Binding Kunde_Nachname}"></Label>
                                <Label Content=" - "></Label>
                                <Label Content="{Binding Kunde_Vorname}"></Label>
                            </StackPanel>
                        </DataTemplate>
                    </syncfusion:GridComboBoxColumn.CellTemplate>
                </syncfusion:GridComboBoxColumn>

Why is "Binding Kunde_Nachname" and "Binding Kunde_Vorname" not working? With DisplayMemberPath everything works fine.

Thanks for ur help.

Best regards
Steve

Loader.
Up arrow icon