WPF DataGrid Remove Column

Question

I have created a DataGrid in WPF from a DataTable with AutoGenerateColumns = true . In the VM I have a command property for adding and deleting columns which manipulates the underlying DataTable.

When I call AddColumn from the main XAML window via Command="{Binding AddColumn}" it works as expected but when I call the RemoveColumn from a resource file with a context menu it calls the command property (im able to step through the code) but does not update the Grid.

<MenuItem Header="Delete" Command="{Binding Source={StaticResource AppViewModel}, Path=DeleteColumn}" CommandParameter="{Binding}" />

I now updated both commands to only set the DataTable to null, ie Dt = null and for the AddColumn this works as expected and removed the Grid and columns but for the RemoveColumn it does nothing... I also see no errors in the output window in regard to binding and when stepping through the code the property is called. I also tried to set the column to invisible which also did not work.

UPDATE

I call the DeleteColumn from the following (simplified) code in a resources file.

<Style x:Key="ColumnHeaderStyle" TargetType="{x:Type DataGridColumnHeader}">
    <Setter Property="VerticalContentAlignment" Value="Center" />
    <Style.Triggers>
        <DataTrigger Binding="{Binding Content, ConverterParameter=*, Converter={StaticResource AfterDashConverter}, RelativeSource={RelativeSource self}}" Value="Green">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type DataGridColumnHeader}">
                        <Grid>
                            <Grid.ContextMenu>
                                <ContextMenu>
                                    <MenuItem Header="Delete" Command="{Binding Source={StaticResource AppViewModel}, Path=DeleteColumn}" />
                                </ContextMenu>
                            </Grid.ContextMenu>
                            <DataGridColumnHeader x:Name="PART_FillerColumnHeader" IsHitTestVisible="False"/>
                            <ItemsPresenter/>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </DataTrigger>
    </Style.Triggers>
</Style>

The commands are very simple, the AddColumn works as its directly in my main view and the DeleteColumn does not as its in the above resource file. I have checked the commands fire properly.

    AddColumn = new RelayCommand(_ =>
    {
        Dt = null;
    }, true);

    DeleteColumn = new RelayCommand(column =>
    {
        Dt = null;
    }, true);

Answer 1

the main issue was my resource was creating a new viewmodel so it was not calling / impacting the VM instance that my view was dependent on. To fix this I needed to set the DataContext of my ContextMenu parent control (which was a grid) as follows:

DataContext="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type MyType}}}

If you just call the following it will create a new instance of your ViewModel and use that:

<MenuItem Header="Delete" Command="{Binding Source={StaticResource AppViewModel}, Path=DeleteColumn}" />