Xml bind + Command Buttons?

[ITA]

Hi,

i have a working RadGridView with an XML-File which is bind by XMLDataProvider. I want to use a Telerik RadButton with a Command to insert, delete or edit Rows. But it does not work:

CODE:
                                                        <StackPanel Grid.Row="0" Orientation="Horizontal" HorizontalAlignment="left" Margin="0,5,0,0">
                                                            <telerik:RadButton Width="100" Content="Delete selected rows" Margin="0,0,5,0"
                                                                                Command="telerikGrid:RadGridViewCommands.Delete" CommandTarget="{Binding ElementName=radGridView2}"  />
                                                            <telerik:RadButton Width="100" Content="Add new row" Margin="0,0,5,0"
                                                                                Command="telerikGrid:RadGridViewCommands.BeginInsert" CommandTarget="{Binding ElementName=radGridView2}"  />
                                                            <telerik:RadButton Width="100" Content="Save insert/edit" Margin="0,0,5,0"
                                                                                Command="telerikGrid:RadGridViewCommands.CommitEdit" CommandTarget="{Binding ElementName=radGridView2}"  />
                                                            <telerik:RadButton Width="100" Content="Cancel insert/edit"
                                                                                Command="telerikGrid:RadGridViewCommands.CancelRowEdit" CommandTarget="{Binding ElementName=radGridView2}"  />
                                                        </StackPanel>
                                                        <Grid Grid.Row="1">                                                           
                                                            <Grid.Resources>
                                                                <XmlDataProvider x:Key="MADSource" Source="settings\mandanten.xml" XPath="//Attributes/Attribute[@AttributeGroup='Mandant']"></XmlDataProvider>
                                                            </Grid.Resources>
                                                            <telerik:RadGridView Visibility="Visible" x:Name="radGridView2" AutoGenerateColumns="False" ItemsSource="{Binding Source={StaticResource MADSource}}"
                                                                                 CanUserDeleteRows="True" CanUserInsertRows="True" IsReadOnly="False" ShowGroupPanel="False" SelectionMode="Extended">
                                                                <telerik:RadGridView.Columns>
                                                                    <telerik:GridViewDataColumn DataMemberBinding="{Binding XPath=ContentAttribute[@AttributeName\=\Name] }" Header="Name" Width="120">
                                                                        <telerik:GridViewDataColumn.CellTemplate>
                                                                            <DataTemplate>
                                                                                <ContentControl Content="{Binding XPath=ContentAttribute[@AttributeName\=\'Name\']}">
                                                                                </ContentControl>
                                                                            </DataTemplate>
                                                                        </telerik:GridViewDataColumn.CellTemplate>
                                                                    </telerik:GridViewDataColumn>
                                                                    <telerik:GridViewDataColumn DataMemberBinding="{Binding XPath=ContentAttribute[@AttributeName\=\Host] }" Header="Host" Width="100">
                                                                        <telerik:GridViewDataColumn.CellTemplate>
                                                                            <DataTemplate>
                                                                                <ContentControl Content="{Binding XPath=ContentAttribute[@AttributeName\=\'Host\']}">
                                                                                </ContentControl>
                                                                            </DataTemplate>
                                                                        </telerik:GridViewDataColumn.CellTemplate>
                                                                    </telerik:GridViewDataColumn>
                                                                    <telerik:GridViewDataColumn DataMemberBinding="{Binding XPath=ContentAttribute[@AttributeName\=\Port] }" Header="Port" Width="50">
                                                                        <telerik:GridViewDataColumn.CellTemplate>
                                                                            <DataTemplate>
                                                                                <ContentControl Content="{Binding XPath=ContentAttribute[@AttributeName\=\'Port\']}">
                                                                                </ContentControl>
                                                                            </DataTemplate>
                                                                        </telerik:GridViewDataColumn.CellTemplate>
                                                                    </telerik:GridViewDataColumn>
                                                                </telerik:RadGridView.Columns>
                                                            </telerik:RadGridView>
CODEBEHIND:
    Public Sub New()

        Dim deleteCommand As ICommand = RadGridViewCommands.Delete
        Dim beginInsertCommand As ICommand = RadGridViewCommands.BeginInsert
        Dim cancelRowEditCommand As ICommand = RadGridViewCommands.CancelRowEdit
        Dim commitEditCommand As ICommand = RadGridViewCommands.CommitEdit

        InitializeComponent()
    End Sub

I get no errors, but the buttons do not work and i can't edit the Columns. HELP!!!
Rene