Detect when Listview ItemsTemplate usercontrol recycles user control.

Question

I have a virtualizing ListView control with a user control as the items template. When the user control is loaded an async call is made that I'd like to cancel if the user control is out of view. 

I tried using Unloaded but this is not called, even though the items stack panel's cache no longer contains that item. What event will notify the C# when a user control leaves the item stack panels cache, or list view's viewable area?

I tried using container content changing but it only shows which items are coming into view, but does not show when the container items leaves view.

Thank you :)

Here is the XAML.

<ListView ItemsSource="{Binding MyItemsObs}"
                  ContainerContentChanging="ListViewBase_OnContainerContentChanging"
                  Loaded="ListView_OnLoaded"
                  Style="{StaticResource ListViewStyle1}">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <local:MyItemUC/>
                </DataTemplate>
            </ListView.ItemTemplate>
</ListView>

You can get the items stack panel by adding a loaded event in the listview template, or use some visual tree helper extension like win rt xaml toolkit. 

private void FrameworkElement_OnLoaded(object sender, RoutedEventArgs e)
{
    _itemsStackPanel = sender as ItemsStackPanel;
    _itemsStackPanel.CacheLength = 0;
}

Answer 1

Posting for anyone that's using this as a reference.

There's a method in my user control which is called in phase 1 of container content changing. Inside of this method on the UC, pass in a guid/or the list view item's view model. Then the UC can check if the value is different. If the value is different I am going to cancel the task in the old view model.

Answer 2

Thank you for sharing your solution with us :) Should help someone who meet the same issue.

--James

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