Observable.DefaultIfEmpty<TSource> Method (IObservable<TSource>, 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), _
    defaultValue As TSource _
) As IObservable(Of TSource)

'Usage
Dim source As IObservable(Of TSource)
Dim defaultValue As TSource
Dim returnValue As IObservable(Of TSource)

returnValue = source.DefaultIfEmpty(defaultValue)

public static IObservable<TSource> DefaultIfEmpty<TSource>(
    this IObservable<TSource> source,
    TSource defaultValue
)

[ExtensionAttribute]
public:
generic<typename TSource>
static IObservable<TSource>^ DefaultIfEmpty(
    IObservable<TSource>^ source, 
    TSource defaultValue
)

static member DefaultIfEmpty : 
        source:IObservable<'TSource> * 
        defaultValue:'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 the specified value for if it is empty.

• defaultValue
  Type: TSource
  The value to return if the sequence is empty.

Return Value

Type: System.IObservable<TSource>
An observable sequence that contains the specified default value 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 .

See Also

Reference

Observable Class

DefaultIfEmpty Overload

System.Reactive.Linq Namespace