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

Observable.Count(IObservable) method¶

Defined in

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

Applies to

netstandard2.0

Overloads¶

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

1. Overload¶

public static IObservable<int> Count<TSource>(this IObservable<TSource> source)

Summary: Returns an observable sequence containing an Int32 that represents the total number of elements in an observable sequence.

Type parameters

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

Parameters

Name	Type	Description
`source`	IObservable	An observable sequence that contains elements to be counted.

Returns: IObservable -- An observable sequence containing a single element with the number of elements in the input sequence.

Remarks

The return type of this operator differs from the corresponding operator on IEnumerable in order to retain asynchronous behavior.

Exceptions

Type	Condition
System.ArgumentNullException	`source` is null.
System.OverflowException	(Asynchronous) The number of elements in the source sequence is larger than MaxValue.

2. Overload¶

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

Summary: Returns an observable sequence containing an Int32 that represents how many elements in the specified observable sequence satisfy a condition.

Type parameters

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

Parameters

Name	Type	Description
`source`	IObservable	An observable sequence that contains elements to be counted.
`predicate`	Func	A function to test each element for a condition.

Returns: IObservable -- An observable sequence containing a single element with a number that represents how many elements in the input sequence satisfy the condition in the predicate function.

Remarks

The return type of this operator differs from the corresponding operator on IEnumerable in order to retain asynchronous behavior.

Exceptions

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