)} ,System.Func{--0,System.Boolean})}

Observable.FirstAsync(IObservable) method¶

Defined in

Type: Observable Namespace: System.Reactive.Linq Assembly: System.Reactive.dll

Applies to

netstandard2.0

Overloads¶

1. public static IObservable<TSource> FirstAsync<TSource>(this IObservable<TSource> source)
2. public static IObservable<TSource> FirstAsync<TSource>(this IObservable<TSource> source, Func<TSource, bool> predicate)

public static IObservable<TSource> FirstAsync<TSource>(this IObservable<TSource> source)

Summary: Returns the first element of an observable sequence.

Type parameters

Name	Description
`TSource`	The type of the elements in the source sequence.

Parameters

Name	Type	Description
`source`	IObservable	Source observable sequence.

Returns: IObservable -- Sequence containing the first element in the observable sequence.

Exceptions

Type	Condition
System.ArgumentNullException	`source` is null.
System.InvalidOperationException	(Asynchronous) The source sequence is empty.

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

Summary: Returns the first element of an observable sequence that satisfies the condition in the predicate.

Type parameters

Name	Description
`TSource`	The type of the elements in the source sequence.

Parameters

Name	Type	Description
`source`	IObservable	Source observable sequence.
`predicate`	Func	A predicate function to evaluate for elements in the source sequence.

Returns: IObservable -- Sequence containing the first element in the observable sequence that satisfies the condition in the predicate.

Exceptions

Type	Condition
System.ArgumentNullException	`source` or `predicate` is null.
System.InvalidOperationException	(Asynchronous) No element satisfies the condition in the predicate. -or- The source sequence is empty.