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

<ExtensionAttribute> _
Public Shared Function GroupBy(Of TSource, TKey, TElement) ( _
	source As IObservable(Of TSource), _
	keySelector As Func(Of TSource, TKey), _
	elementSelector As Func(Of TSource, TElement), _
	comparer As IEqualityComparer(Of TKey) _
) As IObservable(Of IGroupedObservable(Of TKey, TElement))
Dim source As IObservable(Of TSource)
Dim keySelector As Func(Of TSource, TKey)
Dim elementSelector As Func(Of TSource, TElement)
Dim comparer As IEqualityComparer(Of TKey)
Dim returnValue As IObservable(Of IGroupedObservable(Of TKey, TElement))

returnValue = source.GroupBy(keySelector, _
	elementSelector, comparer)

Type Parameters


The type source.


The type key.


The type element.


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

Return Value

Type: System.IObservable(Of IGroupedObservable(Of 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(Of 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.