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

Observable.FirstOrDefault(IObservable) method¶

Defined in

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

Applies to

netstandard2.0

Overloads¶

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

1. Overload¶

Deprecated

This blocking operation is no longer supported. Instead, use the async version in combination with C# and Visual Basic async/await support. In case you need a blocking operation, use Wait or convert the resulting observable sequence to a Task object and block.

Attributes: [Obsolete("This blocking operation is no longer supported. Instead, use the async version in combination with C# and Visual Basic async/await support. In case you need a blocking operation, use Wait or convert the resulting observable sequence to a Task object and block.")]

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

Summary: Returns the first element of an observable sequence, or a default value if no such element exists.

Type parameters

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

Parameters

Name	Type	Description
`source`	IObservable	Source observable sequence.

Returns: TSource -- The first element in the observable sequence, or a default value if no such element exists.

Exceptions

Type	Condition
System.ArgumentNullException	`source` is null.

See also

System.Reactive.Linq.Observable.FirstOrDefaultAsync1(System.IObservable{0})

2. Overload¶

Deprecated

This blocking operation is no longer supported. Instead, use the async version in combination with C# and Visual Basic async/await support. In case you need a blocking operation, use Wait or convert the resulting observable sequence to a Task object and block.

Attributes: [Obsolete("This blocking operation is no longer supported. Instead, use the async version in combination with C# and Visual Basic async/await support. In case you need a blocking operation, use Wait or convert the resulting observable sequence to a Task object and block.")]

public static TSource FirstOrDefault<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, or a default value if no such element exists.

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: TSource -- The first element in the observable sequence that satisfies the condition in the predicate, or a default value if no such element exists.

Exceptions

Type	Condition
System.ArgumentNullException	`source` or `predicate` is null.

See also

System.Reactive.Linq.Observable.FirstOrDefaultAsync1(System.IObservable{0},System.Func{``0,System.Boolean})