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Queryable.Except(Of TSource) Method (IQueryable(Of TSource), IEnumerable(Of TSource))

Produces the set difference of two sequences by using the default equality comparer to compare values.

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

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

Type Parameters

TSource

The type of the elements of the input sequences.

Parameters

source1
Type: System.Linq.IQueryable(Of TSource)

An IQueryable(Of T) whose elements that are not also in source2 will be returned.

source2
Type: System.Collections.Generic.IEnumerable(Of TSource)

An IEnumerable(Of T) whose elements that also occur in the first sequence will not appear in the returned sequence.

Return Value

Type: System.Linq.IQueryable(Of TSource)
An IQueryable(Of 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(Of 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 Nothing.

The Except(Of TSource)(IQueryable(Of TSource), IEnumerable(Of TSource)) method generates a MethodCallExpression that represents calling Except(Of TSource)(IQueryable(Of TSource), IEnumerable(Of TSource)) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery(Of 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(Of TSource)(IQueryable(Of TSource), IEnumerable(Of 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.

The following code example demonstrates how to use Except(Of TSource)(IQueryable(Of TSource), IEnumerable(Of TSource)) to return those elements that only appear in the first source sequence.

        Dim numbers1() As Double = {2.0, 2.1, 2.2, 2.3, 2.4, 2.5}
        Dim numbers2() As Double = {2.2}

        ' Get the numbers from the first array that 
        ' are NOT in the second array. 
        Dim onlyInFirstSet As IEnumerable(Of Double) = _
            numbers1.AsQueryable().Except(numbers2)

        Dim output As New System.Text.StringBuilder
        For Each number As Double In onlyInFirstSet
            output.AppendLine(number)
        Next 

        ' Display the output.
        MsgBox(output.ToString())

        ' This code produces the following output: 
        
        ' 2 
        ' 2.1 
        ' 2.3 
        ' 2.4 
        ' 2.5

.NET Framework

Supported in: 4.6, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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