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)

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

Type Parameters


The type of source.


Type: System.IObservable<TSource>
The sequence to return the specified value for if it is empty.
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 https://msdn.microsoft.com/en-us/library/bb384936.aspx or https://msdn.microsoft.com/en-us/library/bb383977.aspx.