Article
11/18/2011

Queryable.Except<TSource> Method (IQueryable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values.

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

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function Except(Of TSource) ( _
    source1 As IQueryable(Of TSource), _
    source2 As IEnumerable(Of TSource), _
    comparer As IEqualityComparer(Of TSource) _
) As IQueryable(Of TSource)

public static IQueryable<TSource> Except<TSource>(
    this IQueryable<TSource> source1,
    IEnumerable<TSource> source2,
    IEqualityComparer<TSource> comparer
)

Type Parameters

TSource
The type of the elements of the input sequences.

Parameters

source1
Type: System.Linq.IQueryable<TSource>
An IQueryable<T> whose elements that are not also in source2 will be returned.

source2
Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> whose elements that also occur in the first sequence will not appear in the returned sequence.

comparer
Type: System.Collections.Generic.IEqualityComparer<TSource>
An IEqualityComparer<T> to compare values.

Return Value

Type: System.Linq.IQueryable<TSource>
An IQueryable<T> that contains the set difference of the two sequences.

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.

Exceptions

Exception	Condition
ArgumentNullException	source1 or source2 is nulla null reference (Nothing in Visual Basic).

Remarks

The Except<TSource>(IQueryable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>) method generates a MethodCallExpression that represents calling Except<TSource>(IQueryable<TSource>, IEnumerable<TSource>, IEqualityComparer<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 thesource1 parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Except<TSource>(IQueryable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>) depends on the implementation of the type of the source1 parameter. The expected behavior is that all the elements in source1 are returned except for those that are also in source2, and comparer is used to compare values.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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