WPF - hiding listbox items

Question

I have a listbox where the itemtemplate is using a style. The styles specifies a border with a datatrigger setting the visibility of the border to collapsed depending on a property. This works fine except I can still see a very narrow line for each item, in the list, that is collapsed. I was hoping someone could help with how to set the visibility so that there are no visible traces as this is quite apparent when consecutive items have been collapsed.

The datatemplate specifies an outer border with a dockpanel inside of this - there are then stackpanels docked to this.

Any help is appreciated.

Well this is a simplified template:

<DataTemplate x:Key="myTemplate">
    <Border BorderThickness="0">
        <Border.Style>
            <Style>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Path=IsActive}" Value="False">
                        <Setter Property="Border.Visibility" Value="Collapsed" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Border.Style>
        <DockPanel LastChildFill="True" HorizontalAlignment="Stretch">
            <StackPanel DockPanel.Dock="Right" HorizontalAlignment="Right"  >
                <TextBlock Text="{Binding Path=SeqNo, Converter={StaticResource SeqToTextConv}}"/>
                <Label Content="..." />
            </StackPanel>
        </DockPanel>
    </Border>
</DataTemplate>

Answer 1

You are succesfully hiding your item, however, the ListBox wraps each of your items within a ListBoxItem, this adds concepts such as selection to your item. I suspect you are still seeing the ListBoxItem in the case where your items are hidden. You can use the ItemContainerStyle to hide ListBoxItems ...

<ListBox>
  <ListBox.ItemContainerStyle>
    <Style TargetType="{x:Type ListBoxItem}">
      <Style.Triggers>
        <DataTrigger Binding="{Binding IsActive}" Value="False">
          <Setter Property="Visibility" Value="Collapsed"/>
        </DataTrigger>
      </Style.Triggers>
    </Style>
  </ListBox.ItemContainerStyle>
</ListBox>

Answer 2

This can also be achieved by populating ListBox.Items only with ListBoxItem instead of other controls:

ListBox.Items.Add(new ListBoxItem { 
    Content = new CheckBox {Content = "item 1"} 
    })

or

<ListBox>
    <ListBox.Items>
        <ListBoxItem>
            <CheckBox Content="item 1"/>
        </ListBoxItem>
    </ListBox.Items>
</ListBox>

Then in the code behind or in the trigger, you can hide the items directly:

ListBox.Items[0].Visibility = Visibility.Collapse

This will hide the item as well as the 4px border. This method gives you control of visibility for each individual item.