Binding a context menu command parameter to a datagrid property

Question

In my XAML file I have a DataGrid with a context menu. The data source is a ViewModel which has a property EntityCollection (an ObservableCollection) as the ItemsSource of the DataGrid and another collection ContextMenu.MenuItems which serves as the data source to create a context menu on the DataGrid. The elements of that collection have a Command property which I bind to the Command property of the menu items:

<DataGrid Name="EntityDataGrid" ItemsSource="{Binding EntityCollection}" Height="450">
  <DataGrid.ContextMenu>
    <ContextMenu ItemsSource="{Binding Path=ContextMenu.MenuItems}">
      <ContextMenu.ItemContainerStyle>
        <Style TargetType="{x:Type MenuItem}">
          <Setter Property="Command" Value="{Binding Command}" />
          <Setter Property="CommandParameter"
                  Value="{Binding ElementName=EntityDataGrid, Path=SelectedItems}" />
        </Style>
      </ContextMenu.ItemContainerStyle>
    </ContextMenu>
  </DataGrid.ContextMenu>
</DataGrid>

The action for the menu item command has the following signature in the ViewModel:

private void SelectedItemsAction(object parameter)
{
    // Do something with "parameter"
}

Now my problem is that I reach SelectedItemsAction when I click on a context menu item but the parameter is null. I believe that my problem is in the setter for the CommandParameter property. As you can see, I want to bind this property to the SelectedItems property of the DataGrid by setting the value to:

<Setter Property="CommandParameter"
        Value="{Binding ElementName=EntityDataGrid, Path=SelectedItems}" />

I've tried simpler values as a test:

<Setter Property="CommandParameter"
        Value="{Binding ElementName=EntityDataGrid, Path=Height}" />

Here parameter is still null. And then just to test if any parameter reaches my action method at all:

<Setter Property="CommandParameter"
        Value="10" />

This works, the parameter in my action method is now indeed 10.

What am I doing wrong to bind the CommandParameter value to a property of EntityDataGrid? Is it possible at all?

Thank you for help in advance!

Answer 1

Have you tried doing an Ancestor binding? Something like:

<Setter Property="CommandParameter"
        Value="{Binding Path=SelectedItems, 
        RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}" />