/// <summary> Invokes the specified handler when a collection property on a property changes, when the source changes,
/// or when the collection changes. </summary>
/// <param name="propertyName"> The name of the property on the source. </param>
/// <param name="collectionPropertyOnPropertyName"> The name of the collection property on the property on the source, i.e. <code>source.property.collectionProperty</code></param>
/// <param name="handler"> The handler to be invoked at the moments listed above. </param>
public static void BindCollection(this INotifyPropertyChanged source, string propertyName, string collectionPropertyOnPropertyName, NotifyCollectionChangedEventHandler handler)
{
Contract.Requires(GetPropertyType(source.GetType(), propertyName, collectionPropertyOnPropertyName).Implements(typeof(INotifyCollectionChanged)), $"The collection property '{collectionPropertyOnPropertyName}' on the source must implement '{nameof(INotifyCollectionChanged)}'");
source.Bind(propertyName, collectionPropertyOnPropertyName, RebindCollectionChangedHandler);
void RebindCollectionChangedHandler(object sender, PropertyChangedEventArgs eventArg)
{
IPropertyMutatedEventArgs e = (IPropertyMutatedEventArgs)eventArg;
Contract.Requires(sender != null);
Contract.Requires(e != null);
Contract.Requires(e.OldValue == null || e.OldValue.GetType().Implements(typeof(INotifyCollectionChanged)), "The collection instance must implement 'INotifyCollectionChanged'");
Contract.Requires(e.NewValue == null || e.NewValue.GetType().Implements(typeof(INotifyCollectionChanged)), "The collection instance must implement 'INotifyCollectionChanged'");
Contract.Requires(e.OldValue == null || e.OldValue.GetType().Implements(typeof(System.Collections.IList)), "The collection instance must implement 'IList'");
Contract.Requires(e.NewValue == null || e.NewValue.GetType().Implements(typeof(System.Collections.IList)), "The collection instance must implement 'IList'");
if (e.OldValue is INotifyCollectionChanged oldCollection)
{
oldCollection.CollectionChanged -= handler;
}
if (e.NewValue is INotifyCollectionChanged newCollection)
{
newCollection.CollectionChanged += handler;
handler(sender, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, newCollection, e.OldValue as System.Collections.IList));
}
}
}
private static Action ForwardPropertyChanged(this INotifyPropertyChanged source, ImmutableQueue <JsonPathNode> dependencyNodes, INotifyPropertyChanged target, string targetPropertyName)
{
WeakReference <INotifyPropertyChanged> wr = new WeakReference <INotifyPropertyChanged>(target);
Action unsubscribe = null;
dependencyNodes = dependencyNodes.Dequeue(out var node);
switch (node)
{
case JsonPathPropertySelectorNode propertySelectorNode:
string sourcePropertyName = propertySelectorNode.PropertyName;
unsubscribe = source.ForwardPropertyChanged(sourcePropertyName, target, targetPropertyName);
if (dependencyNodes.IsEmpty)
{
return(unsubscribe);
}
Action unsubscribeNested = null;
if (propertySelectorNode.GetValue(source) is INotifyPropertyChanged nestedSource)
{
unsubscribeNested = nestedSource.ForwardPropertyChanged(dependencyNodes, target, targetPropertyName);
unsubscribe += unsubscribeNested;
}
unsubscribe += source.Bind <INotifyPropertyChanged, object>(sourcePropertyName, (value) =>
{
unsubscribe -= unsubscribeNested;
unsubscribeNested?.Invoke();
if (!wr.TryGetTarget(out var t))
{
return;
}
if (value is INotifyPropertyChanged nestedSrc)
{
unsubscribeNested = nestedSrc.ForwardPropertyChanged(dependencyNodes, t, targetPropertyName);
unsubscribe += unsubscribeNested;
}
});
