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MSDN Library

Queryable.Union<TSource> Method (IQueryable<TSource>, IEnumerable<TSource>)

Produces the set union of two sequences by using the default equality comparer.

Namespace:  System.Linq
Assemblies:   System.Linq.Queryable (in System.Linq.Queryable.dll)
  System.Core (in System.Core.dll)

public static IQueryable<TSource> Union<TSource>(
	this IQueryable<TSource> source1,
	IEnumerable<TSource> source2
)

Type Parameters

TSource

The type of the elements of the input sequences.

Parameters

source1
Type: System.Linq.IQueryable<TSource>

A sequence whose distinct elements form the first set for the union operation.

source2
Type: System.Collections.Generic.IEnumerable<TSource>

A sequence whose distinct elements form the second set for the union operation.

Return Value

Type: System.Linq.IQueryable<TSource>
An IQueryable<T> that contains the elements from both input sequences, excluding duplicates.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable<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).

ExceptionCondition
ArgumentNullException

source1 or source2 is null.

The Union<TSource>(IQueryable<TSource>, IEnumerable<TSource>) method generates a MethodCallExpression that represents calling Union<TSource>(IQueryable<TSource>, IEnumerable<TSource>) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source1 parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Union<TSource>(IQueryable<TSource>, IEnumerable<TSource>) depends on the implementation of the type of the source1 parameter. The expected behavior is that the set union of the elements in source1 and source2 is returned.

The following code example demonstrates how to use Union<TSource>(IQueryable<TSource>, IEnumerable<TSource>) to obtain the set union of two sequences.

            int[] ints1 = { 5, 3, 9, 7, 5, 9, 3, 7 };
            int[] ints2 = { 8, 3, 6, 4, 4, 9, 1, 0 };

            // Get the set union of the items in the two arrays.
            IEnumerable<int> union = ints1.AsQueryable().Union(ints2);

            foreach (int num in union)
                Console.Write("{0} ", num);

            /*
                This code produces the following output:

                5 3 9 7 8 6 4 1 0
            */

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library
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