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

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

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), _
    comparer As IEqualityComparer(Of TKey) _
) As IObservable(Of IGroupedObservable(Of TKey, TSource))
Dim source As IObservable(Of TSource)
Dim keySelector As Func(Of TSource, TKey)
Dim comparer As IEqualityComparer(Of TKey)
Dim returnValue As IObservable(Of IGroupedObservable(Of TKey, TSource))

returnValue = source.GroupBy(keySelector, _
public static IObservable<IGroupedObservable<TKey, TSource>> GroupBy<TSource, TKey>(
    this IObservable<TSource> source,
    Func<TSource, TKey> keySelector,
    IEqualityComparer<TKey> comparer
generic<typename TSource, typename TKey>
static IObservable<IGroupedObservable<TKey, TSource>^>^ GroupBy(
    IObservable<TSource>^ source, 
    Func<TSource, TKey>^ keySelector, 
    IEqualityComparer<TKey>^ comparer
static member GroupBy : 
        source:IObservable<'TSource> * 
        keySelector:Func<'TSource, 'TKey> * 
        comparer:IEqualityComparer<'TKey> -> IObservable<IGroupedObservable<'TKey, 'TSource>> 
JScript does not support generic types and methods.

Type Parameters

  • TSource
    The type source.
  • TKey
    The type key.


  • 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.

Return Value

Type: System.IObservable<IGroupedObservable<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<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see or .

See Also


Observable Class

GroupBy Overload

System.Reactive.Linq Namespace