ObservableCacheEx.WhenPropertyChanged(IObservable<IChangeSet<TObject, TKey>>, Expression<Func<TObject, TValue>>, bool) method

Type: ObservableCacheEx Namespace: DynamicData Assembly: DynamicData.dll

Applies to

net10.0, net10.0-browserwasm1.0, net10.0-desktop1.0, net9.0, net9.0-browserwasm1.0, net9.0-desktop1.0, net8.0, net8.0-ios17.5, net8.0-maccatalyst17.5, net8.0-macos14.2, net8.0-macos14.5, net8.0-tvos17.2, netstandard2.1, netstandard2.0, net462, net471

public static IObservable<PropertyValue<TObject, TValue>> WhenPropertyChanged<TObject, TKey, TValue>(this IObservable<IChangeSet<TObject, TKey>> source, Expression<Func<TObject, TValue>> propertyAccessor, bool notifyOnInitialValue = true) where TObject : INotifyPropertyChanged where TKey : notnull

View source

Summary: Emits a PropertyValue (item + property value) whenever the specified property changes on any item in the cache. Subscribes via INotifyPropertyChanged using MergeMany.

Type parameters

Name	Description
`TObject`	The type of the object (must implement INotifyPropertyChanged).
`TKey`	The type of the key.
`TValue`	The type of the monitored property.

Parameters

Name	Type	Description
`source`	IObservable>	The source `IObservable<IChangeSet<TObject, TKey>>` to observe a specific property on items in.
`propertyAccessor`	Expression>	A Expression that expression selecting the property to monitor.
`notifyOnInitialValue = true`	bool	When `true` (the default), the current property value is emitted immediately for each item upon subscription.

Returns: IObservable> -- An observable of PropertyValue containing both the item and its property value.

Remarks

Per-item subscriptions are created on Add, replaced on Update, disposed on Remove. Errors from individual property subscriptions are silently ignored. The output is not a changeset stream. If you only need the value (not the owning item), use WhenValueChanged instead.

Event	Behavior
Add	Subscribes to the specified property on the new item. If `notifyOnInitialValue` is true, the current value is emitted immediately.
Update	Disposes the old item's property subscription and subscribes to the new item.
Remove	Disposes the item's property subscription. No further emissions for this item.
Refresh	No effect on subscriptions. The existing property subscription continues.
OnError	Per-item property subscription errors are silently ignored. Source errors terminate the stream.

See also

DynamicData.ObservableListEx.WhenPropertyChanged2(System.IObservable{DynamicData.IChangeSet{0}},System.Linq.Expressions.Expression{System.Func{0,1}},System.Boolean)