Set Operations

Set operations in LINQ refer to query operations that produce a result set that is based on the presence or absence of equivalent elements within the same or separate collections (or sets).

The standard query operator methods that perform set operations are listed in the following section.

Methods

Method Name	Description	C# Query Expression Syntax	Visual Basic Query Expression Syntax	More Information
Distinct	Removes duplicate values from a collection.	Not applicable.	Distinct	Enumerable.Distinct Queryable.Distinct
Except	Returns the set difference, which means the elements of one collection that do not appear in a second collection.	Not applicable.	Not applicable.	Enumerable.Except Queryable.Except
Intersect	Returns the set intersection, which means elements that appear in each of two collections.	Not applicable.	Not applicable.	Enumerable.Intersect Queryable.Intersect
Union	Returns the set union, which means unique elements that appear in either of two collections.	Not applicable.	Not applicable.	Enumerable.Union Queryable.Union

Comparison of Set Operations

Distinct

The following illustration depicts the behavior of the Enumerable.Distinct method on a sequence of characters. The returned sequence contains the unique elements from the input sequence.

Except

The following illustration depicts the behavior of Enumerable.Except. The returned sequence contains only the elements from the first input sequence that are not in the second input sequence.

Intersect

The following illustration depicts the behavior of Enumerable.Intersect. The returned sequence contains the elements that are common to both of the input sequences.

Union

The following illustration depicts a union operation on two sequences of characters. The returned sequence contains the unique elements from both input sequences.

Query Expression Syntax Example

The following example uses the Distinct clause (available in Visual Basic only) in a LINQ query to return the unique numbers from a list of integers.

Dim classGrades = New System.Collections.Generic.List(Of Integer) From {63, 68, 71, 75, 68, 92, 75}

        Dim distinctQuery = From grade In classGrades 
                            Select grade Distinct

        Dim sb As New System.Text.StringBuilder("The distinct grades are: ")
        For Each number As Integer In distinctQuery
            sb.Append(number & " ")
        Next 

        ' Display the results.
        MsgBox(sb.ToString())

        ' This code produces the following output: 

        ' The distinct grades are: 63 68 71 75 92 

See Also

Tasks

How to: Combine and Compare String Collections (LINQ)

How to: Find the Set Difference Between Two Lists (LINQ)

Reference

Distinct Clause (Visual Basic)

System.Linq

Concepts

Standard Query Operators Overview