Observable.ToLookup<TSource, TKey, TElement> Method (IObservable<TSource>, Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>)
Creates a lookup from an observable sequence according to a specified key selector function, a comparer, and an element selector function.
Namespace: System.Reactive.Linq
Assembly: System.Reactive (in System.Reactive.dll)
Syntax
'Declaration
<ExtensionAttribute> _
Public Shared Function ToLookup(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 ILookup(Of TKey, TElement))
'Usage
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 ILookup(Of TKey, TElement))
returnValue = source.ToLookup(keySelector, _
elementSelector, comparer)
public static IObservable<ILookup<TKey, TElement>> ToLookup<TSource, TKey, TElement>(
this IObservable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector,
IEqualityComparer<TKey> comparer
)
[ExtensionAttribute]
public:
generic<typename TSource, typename TKey, typename TElement>
static IObservable<ILookup<TKey, TElement>^>^ ToLookup(
IObservable<TSource>^ source,
Func<TSource, TKey>^ keySelector,
Func<TSource, TElement>^ elementSelector,
IEqualityComparer<TKey>^ comparer
)
static member ToLookup :
source:IObservable<'TSource> *
keySelector:Func<'TSource, 'TKey> *
elementSelector:Func<'TSource, 'TElement> *
comparer:IEqualityComparer<'TKey> -> IObservable<ILookup<'TKey, 'TElement>>
JScript does not support generic types and methods.
Type Parameters
- TSource
The type of source.
- TKey
The type of key.
- TElement
The type of element.
Parameters
- source
Type: System.IObservable<TSource>
An observable sequence to create a lookup for.
- keySelector
Type: System.Func<TSource, TKey>
A function to extract a key from each element.
- elementSelector
Type: System.Func<TSource, TElement>
A transform function to produce a result element value from each element.
- comparer
Type: System.Collections.Generic.IEqualityComparer<TKey>
An equality comparer to compare keys.
Return Value
Type: System.IObservable<ILookup<TKey, TElement>>
A lookup from an observable sequence according to a specified key selector function, a comparer, and an element 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 .