Observable.DistinctUntilChanged<TSource, TKey> Method (IObservable<TSource>, Func<TSource, TKey>)

Returns an observable sequence that contains only distinct contiguous elements according to the keySelector.

Namespace:  System.Reactive.Linq
Assembly:  System.Reactive (in System.Reactive.dll)

public static IObservable<TSource> DistinctUntilChanged<TSource, TKey>(
	this IObservable<TSource> source,
	Func<TSource, TKey> keySelector

Type Parameters


The type of source.


The type of key.


Type: System.IObservable<TSource>
An observable sequence to retain distinct contiguous elements for, based on a computed key value.
Type: System.Func<TSource, TKey>
A function to compute the comparison key for each element.

Return Value

Type: System.IObservable<TSource>
An observable sequence only containing the distinct contiguous elements, based on a computed key value from the source sequence.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IObservable<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see https://msdn.microsoft.com/en-us/library/bb384936(v=vs.103).aspx or https://msdn.microsoft.com/en-us/library/bb383977(v=vs.103).aspx.