Deleting row in listview using Command + CommandParameter in WPF + MVVM - wpf

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.

Answer 2

As long as your button's Tag isn't null (if it is null, you have a different problem), I don't see a reason that you can't bind directly to CriterionId like you do with Tag.