ParallelEnumerable.SingleOrDefault(Of TSource) Method (ParallelQuery(Of TSource), Func(Of TSource, Boolean))

.NET Framework (current version)

Returns the only element of a parallel sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

Public Shared Function SingleOrDefault(Of TSource) (
	source As ParallelQuery(Of TSource),
	predicate As Func(Of TSource, Boolean)
) As TSource


Type: System.Linq.ParallelQuery(Of TSource)

The sequence to return the single element of.

Type: System.Func(Of TSource, Boolean)

A function to test an element for a condition.

Return Value

Type: TSource

The single element of the input sequence that satisfies the condition, or default() if no such element is found.

Type Parameters


The type of the elements of source.

Exception Condition

The query was canceled with the token passed in through WithCancellation.


source or predicate is a null reference (Nothing in Visual Basic).


One or more exceptions occurred during the evaluation of the query.


source is empty or multiple elements are returned.

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1
Return to top