Observable.DefaultIfEmpty<TSource> Method (IObservable<TSource>)
Returns the elements of the specified sequence or the type parameter's default value in a singleton sequence if the sequence is empty.
Namespace: System.Reactive.Linq
Assembly: System.Reactive (in System.Reactive.dll)
Syntax
'Declaration
<ExtensionAttribute> _
Public Shared Function DefaultIfEmpty(Of TSource) ( _
source As IObservable(Of TSource) _
) As IObservable(Of TSource)
'Usage
Dim source As IObservable(Of TSource)
Dim returnValue As IObservable(Of TSource)
returnValue = source.DefaultIfEmpty()
public static IObservable<TSource> DefaultIfEmpty<TSource>(
this IObservable<TSource> source
)
[ExtensionAttribute]
public:
generic<typename TSource>
static IObservable<TSource>^ DefaultIfEmpty(
IObservable<TSource>^ source
)
static member DefaultIfEmpty :
source:IObservable<'TSource> -> IObservable<'TSource>
JScript does not support generic types and methods.
Type Parameters
- TSource
The type of source.
Parameters
- source
Type: System.IObservable<TSource>
The sequence to return a default value for if it is empty.
Return Value
Type: System.IObservable<TSource>
An observable sequence that contains the default value for the TSource type if the source is empty; otherwise, the elements of the source itself.
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 or .