/// <summary>
/// Initializes the <see cref="ItemsControl.ItemsSource"/> property with the <see cref="SubItemsProvider"/>.
/// </summary>
/// <returns><c>true</c>, if the <see cref="ItemsControl.ItemsSource"/> property was changed by this method, else <c>false</c>.</returns>
protected virtual bool InitializeSubItemsSource()
{
SubItemsProvider sip = SubItemsProvider;
IEnumerable oldItemsSource = ItemsSource;
if (!_contextChangedAttached)
{
ContextChanged += OnContextChanged;
_contextChangedAttached = true;
}
if (_attachedContextSource != null)
{
_attachedContextSource.Detach(OnDataContextValueChanged);
}
_attachedContextSource = DataContext.EvaluatedSourceValue;
_attachedContextSource.Attach(OnDataContextValueChanged);
object context = Context;
if (context == null)
{
return(false);
}
ItemsSource = sip == null ? null : sip.GetSubItems(context);
if (oldItemsSource == ItemsSource)
{
return(false);
}
MPF.TryCleanupAndDispose(oldItemsSource);
CheckExpandable();
return(true);
}
protected override void PrepareItemsOverride(bool force)
{
SubItemsProvider sip = SubItemsProvider;
if (sip == null)
{
return;
}
if (ItemsSource == null)
{
if (InitializeSubItemsSource()) // This could trigger a recursive call of PrepareItems(true) if the ItemsSource was changed, that's why we set _preventItemsPreparation above
{
force = true;
}
}
base.PrepareItemsOverride(force);
}
