public override object?ProvideValue(IServiceProvider serviceProvider)
{
var rootObjectProvider = (IRootObjectProvider)serviceProvider.GetService(typeof(IRootObjectProvider));
if (rootObjectProvider == null)
{
VisualComposition.OnError(this, $"Import: Service {nameof(IRootObjectProvider)} unavailable.");
return(null);
}
var rootObject = rootObjectProvider.RootObject as FrameworkElement ?? Application.Current.MainWindow;
if (rootObject == null)
{
return(null);
}
if (DesignerProperties.GetIsInDesignMode(rootObject))
{
return(null);
}
if (AllowRecomposition)
{
var provideValueTarget = (IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget));
if (provideValueTarget != null)
{
_targetObject = provideValueTarget.TargetObject;
_targetProperty = provideValueTarget.TargetProperty;
}
_tracker = rootObject.Track(ExportProviderLocator.ExportProviderProperty);
rootObject.Loaded += RootObject_Loaded;
rootObject.Unloaded += RootObject_Unloaded;
}
else
{
_exportProvider = rootObject.GetExportProvider();
}
return(Value);
}
/// <inheritdoc />
/// <summary>
/// Updates this instance.
/// </summary>
protected override void OnUpdate()
{
var regionId = RegionId;
var itemsControl = AssociatedObject;
var selector = itemsControl as Selector;
VisualComposition.OnTrace(this, $"Update {GetType()}, RegionId={regionId}, ItemsControl={itemsControl}");
if (itemsControl == null)
{
return;
}
if (string.IsNullOrEmpty(regionId))
{
itemsControl.ItemsSource = null;
return;
}
var exports = GetExports(regionId);
if (exports == null)
{
VisualComposition.OnTrace(this, $"Update {GetType()}: No exports for RegionId={regionId} found");
return;
}
var exportedItems = exports
.OrderBy(item => item.Metadata?.Sequence)
.Select(item => GetTarget(item.Value))
.ToArray();
VisualComposition.OnTrace(this, $"Update {GetType()}, Found {exportedItems.Length} items");
var currentItems = itemsControl.Items.Cast <object>().ToArray();
if (exportedItems.SequenceEqual(currentItems))
{
ApplyContext(currentItems, CompositionContext);
return;
}
if (selector != null)
{
selector.SelectionChanged -= Selector_SelectionChanged;
DetachSelectables(currentItems);
}
ApplyContext(currentItems.Except(exportedItems), null);
itemsControl.ItemsSource = exportedItems;
ApplyContext(exportedItems, CompositionContext);
if (selector != null)
{
AttachSelectables(exportedItems);
selector.SelectionChanged += Selector_SelectionChanged;
if (ForceSelection && (selector.SelectedIndex == -1) && !selector.Items.IsEmpty)
{
selector.SelectedIndex = 0;
}
}
}
