Observable.First<TSource> Method (IObservable<TSource>)

Returns the first element of an observable sequence with a specified source.

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


<ExtensionAttribute> _
Public Shared Function First(Of TSource) ( _
    source As IObservable(Of TSource) _
) As TSource
Dim source As IObservable(Of TSource)
Dim returnValue As TSource

returnValue = source.First()
public static TSource First<TSource>(
    this IObservable<TSource> source
generic<typename TSource>
static TSource First(
    IObservable<TSource>^ source
static member First : 
        source:IObservable<'TSource> -> 'TSource 
JScript does not support generic types and methods.

Type Parameters

  • TSource
    The type of source.


Return Value

Type: TSource
The first element in the observable sequence.

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

First Overload

System.Reactive.Linq Namespace