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

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Produces the set difference of two sequences by using the default equality comparer 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) _
) As IQueryable(Of TSource)

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

Type Parameters

  • TSource
    The type of the elements of the input sequences.

Parameters

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>) method generates a MethodCallExpression that represents calling Except<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 thesource1 parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Except<TSource>(IQueryable<TSource>, IEnumerable<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.

Examples

The following code example demonstrates how to use Except<TSource>(IQueryable<TSource>, IEnumerable<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.
      outputBlock.Text &= output.ToString() & vbCrLf

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


         double[] numbers1 = { 2.0, 2.1, 2.2, 2.3, 2.4, 2.5 };
         double[] numbers2 = { 2.2 };

         // Get the numbers from the first array that
         // are NOT in the second array.
         IEnumerable<double> onlyInFirstSet =
             numbers1.AsQueryable().Except(numbers2);

         foreach (double number in onlyInFirstSet)
            outputBlock.Text += number + "\n";

         /*
             This code produces the following output:

             2
             2.1
             2.3
             2.4
             2.5
         */

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.