Qbservable.DefaultIfEmpty<TSource> Method (IQbservable<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.Providers (in System.Reactive.Providers.dll)
Syntax
'Declaration
<ExtensionAttribute> _
Public Shared Function DefaultIfEmpty(Of TSource) ( _
source As IQbservable(Of TSource), _
defaultValue As TSource _
) As IQbservable(Of TSource)
'Usage
Dim source As IQbservable(Of TSource)
Dim defaultValue As TSource
Dim returnValue As IQbservable(Of TSource)
returnValue = source.DefaultIfEmpty(defaultValue)
public static IQbservable<TSource> DefaultIfEmpty<TSource>(
this IQbservable<TSource> source,
TSource defaultValue
)
[ExtensionAttribute]
public:
generic<typename TSource>
static IQbservable<TSource>^ DefaultIfEmpty(
IQbservable<TSource>^ source,
TSource defaultValue
)
static member DefaultIfEmpty :
source:IQbservable<'TSource> *
defaultValue:'TSource -> IQbservable<'TSource>
JScript does not support generic types and methods.
Type Parameters
- TSource
The type of source.
Parameters
- source
Type: System.Reactive.Linq.IQbservable<TSource>
The sequence to return a default value for if it is empty.
- defaultValue
Type: TSource
The value to return if the sequence is empty.
Return Value
Type: System.Reactive.Linq.IQbservable<TSource>
A queryable 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 IQbservable<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see or .