Question

I want to delete a row in ListView Control using Command and CommandParameter like below.

<GridViewColumn Header="X">
<GridViewColumn.CellTemplate>
    <DataTemplate>
        <StackPanel>
           <TextBlock Text="{Binding CriteriaId}"/>
           <Button Name="btnDeleteCriterion" Tag="{Binding CriteriaId}" Content="{Binding CriteriaId}" Foreground="Red" FontWeight="Bold" 
                                                             Command="{Binding DeleteCriterionCommand}" 
                                                                        DataContext="{Binding DataContext, RelativeSource={RelativeSource FindAncestor, AncestorType=ListView}}"
                                                             CommandParameter="{Binding RelativeSource={RelativeSource self}, Path=Tag}"
                                                                        />
        <StackPanel>
    </DataTemplate>
</GridViewColumn.CellTemplate>

I am trying to grab the Tag property of the Button and pass it to Command like above and than remove it from list like so.

Edited, above XAML and added a TextBlock which uses the same binding as the Button’s Tag and Content, but somehow Button doesn’t get the value but TextBlock does!?

    public void DeleteCriterion(object criterionId)
    {
        int crtId = (int)criterionId;
        Criterion crt = _criteria.FirstOrDefault((c) => c.CriterionId == crtId);
        if (crt != null)
            _criteria.Remove(crt);
    }

but I always get criterionId parameter as null.

What am I doing wrong?

Answer 1

Since you’re explicitly setting the DataContext within the button, when you’re doing a binding like {Binding SomeProperty} it will assume that SomeProperty is in the DataContext that you just set. Try using a more explicit binding like:

"{Binding RelativeSource={RelativeSource AncestorType=StackPanel}, Path=DataContext.CriteriaId}" 

which will give you the correct DataContext’s CriteriaID like it is for the TextBlock.