This documentation is archived and is not being maintained.

ParallelEnumerable.Union<TSource> Method (ParallelQuery<TSource>, IEnumerable<TSource>)

Note: This API is now obsolete.

This Union overload should never be called. This method is marked as obsolete and always throws NotSupportedException when called.

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

[ObsoleteAttribute("The second data source of a binary operator must be of type System.Linq.ParallelQuery<T> rather than System.Collections.Generic.IEnumerable<T>. To fix this problem, use the AsParallel() extension method to convert the right data source to System.Linq.ParallelQuery<T>.")]
public static ParallelQuery<TSource> Union<TSource>(
	this ParallelQuery<TSource> first,
	IEnumerable<TSource> second

Type Parameters


This type parameter is not used.


Type: System.Linq.ParallelQuery<TSource>
This parameter is not used.
Type: System.Collections.Generic.IEnumerable<TSource>
This parameter is not used.

Return Value

Type: System.Linq.ParallelQuery<TSource>
This overload always throws a NotSupportedException.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type ParallelQuery<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).


The exception that occurs when this method is called.


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


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

This overload exists to disallow usage of Union with a left data source of type ParallelQuery<TSource> and a right data source of type IEnumerable<T>. Otherwise, the Union operator would appear to be binding to the parallel implementation, but would in reality bind to sequential implementation.

.NET Framework

Obsolete (compiler warning) in 4

.NET Framework Client Profile

Obsolete (compiler warning) in 4

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.