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Observable.GroupBy<TSource, TKey, TElement> Method (IObservable<TSource>, Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>)

Groups the elements of an observable sequence according to a specified key selector function and comparer and selects the resulting elements by using a specified function.

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

public static IObservable<IGroupedObservable<TKey, TElement>> GroupBy<TSource, TKey, TElement>(
	this IObservable<TSource> source,
	Func<TSource, TKey> keySelector,
	Func<TSource, TElement> elementSelector,
	IEqualityComparer<TKey> comparer
)

Type Parameters

TSource

The type source.

TKey

The type key.

TElement

The type element.

Parameters

source
Type: System.IObservable<TSource>
An observable sequence whose elements to group.
keySelector
Type: System.Func<TSource, TKey>
A function to extract the key for each element.
elementSelector
Type: System.Func<TSource, TElement>
A function to map each source element to an element in an observable group.
comparer
Type: System.Collections.Generic.IEqualityComparer<TKey>
An equality comparer to compare keys with.

Return Value

Type: System.IObservable<IGroupedObservable<TKey, TElement>>
A sequence of observable groups, each of which corresponds to a unique key value, containing all elements that share that same key value.

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 http://msdn.microsoft.com/en-us/library/bb384936(v=vs.103).aspx or http://msdn.microsoft.com/en-us/library/bb383977(v=vs.103).aspx.
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