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Qbservable.FirstAsync(IQbservable) method

Defined in

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

Applies to

netstandard2.0

Overloads

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

1. Overload

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

Summary: Returns the first element of an observable sequence.

Type parameters

NameDescription
TSourceThe type of the elements in the source sequence.

Parameters

NameTypeDescription
source[IQbservable](#Source observable sequence.

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

Exceptions

TypeCondition
System.ArgumentNullExceptionsource is null.
System.InvalidOperationException(Asynchronous) The source sequence is empty.

2. Overload

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

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

Type parameters

NameDescription
TSourceThe type of the elements in the source sequence.

Parameters

NameTypeDescription
source[IQbservable](#Source observable sequence.
predicateExpression>A predicate function to evaluate for elements in the source sequence.

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

Exceptions

TypeCondition
System.ArgumentNullExceptionsource or predicate is null.
System.InvalidOperationException(Asynchronous) No element satisfies the condition in the predicate. -or- The source sequence is empty.