Observable.First<TSource> Method (IObservable<TSource>, Func<TSource, Boolean>)

Returns the first element of an observable sequence that matches the predicate.

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

public static TSource First<TSource>(
	this IObservable<TSource> source,
	Func<TSource, bool> predicate

Type Parameters


The type of source.


Type: System.IObservable<TSource>
The source observable sequence.
Type: System.Func<TSource, Boolean>
A predicate function to evaluate for elements in the sequence.

Return Value

Type: TSource
The first element of an observable sequence for which the predicate holds.

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 https://msdn.microsoft.com/en-us/library/bb384936.aspx or https://msdn.microsoft.com/en-us/library/bb383977.aspx.