Event fired when item is added to ListView?

Question

I have this XAML:

<ListView Name="NameListView"
          HorizontalAlignment="Stretch"
          VerticalAlignment="Stretch"
          Grid.Column="1">
    <ListView.View>
        <GridView>
            <GridViewColumn>
                <GridViewColumn.DisplayMemberBinding>
                    <MultiBinding StringFormat="{}{0} {1}">
                        <Binding Path="First" />
                        <Binding Path="Last" />
                    </MultiBinding>
                </GridViewColumn.DisplayMemberBinding>
            </GridViewColumn>
        </GridView>
    </ListView.View>
</ListView>

and an ObservableCollection<Name> called "names" binded to the ListView in my code-behind. When a new new name is added to the collection, I want the ListView to change the background color of that newly added name. How do I go about doing it?

Answer 1

You can subscribe to the ItemsChanged event on your listbox.Items property. This is a little tricky because you have to cast it first. The code to subscribe would look like this:

((INotifyCollectionChanged)MainListBox.Items).CollectionChanged +=  ListBox_CollectionChanged;

And then inside that event you can get to your item with code like this:

private void ListBox_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.NewItems.Count > 0)
        {
            Dispatcher.BeginInvoke(() =>
            {
                var newListItem = MainListBox.ItemContainerGenerator.ContainerFromItem(e.NewItems[0]) as Control;
                if (newListItem != null)
                {
                    newListItem.Background = System.Windows.Media.Brushes.Red;
                }
            }, DispatcherPriority.SystemIdle);
        }
    }

Answer 2

Setting the background of a ListViewItem directly is not a good idea because by default a ListView is virtualizing (which is good), that means the controls that make up the items get disposed when scrolled out of view. The easiest way to do this is that i can think of is having a property in your data-object which indicates the New-state, then you can trigger on it.

<ListView.ItemContainerStyle>
    <Style TargetType="{x:Type ListViewItem}">
        <Style.Triggers>
            <DataTrigger Binding="{Binding IsNew}" Value="True">
                <Setter Property="Background" Value="Yellow"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>
</ListView.ItemContainerStyle>

You then can use any logic you want to set that value to false again if you do not consider it new anymore.