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

Creates a lookup from an observable sequence according to a specified key selector function.

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

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function ToLookup(Of TSource, TKey) ( _
    source As IObservable(Of TSource), _
    keySelector As Func(Of TSource, TKey) _
) As IObservable(Of ILookup(Of TKey, TSource))
'Usage
Dim source As IObservable(Of TSource)
Dim keySelector As Func(Of TSource, TKey)
Dim returnValue As IObservable(Of ILookup(Of TKey, TSource))

returnValue = source.ToLookup(keySelector)
public static IObservable<ILookup<TKey, TSource>> ToLookup<TSource, TKey>(
    this IObservable<TSource> source,
    Func<TSource, TKey> keySelector
)
[ExtensionAttribute]
public:
generic<typename TSource, typename TKey>
static IObservable<ILookup<TKey, TSource>^>^ ToLookup(
    IObservable<TSource>^ source, 
    Func<TSource, TKey>^ keySelector
)
static member ToLookup : 
        source:IObservable<'TSource> * 
        keySelector:Func<'TSource, 'TKey> -> IObservable<ILookup<'TKey, 'TSource>> 
JScript does not support generic types and methods.

Type Parameters

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

Parameters

  • keySelector
    Type: System.Func<TSource, TKey>
    A function to extract a key from each element.

Return Value

Type: System.IObservable<ILookup<TKey, TSource>>
A lookup from an observable sequence according to a specified key selector function.

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

Reference

Observable Class

ToLookup Overload

System.Reactive.Linq Namespace