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

Groups the elements of an observable sequence according to a specified key selector function.

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

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

returnValue = source.GroupBy(keySelector)

Type Parameters


The type source.


The type key.


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.

Return Value

Type: System.IObservable(Of IGroupedObservable(Of TKey, TSource))
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.