Set Operations

Set Operations

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This page is specific to

Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

Microsoft Visual Studio 2010/.NET Framework 4.0

Language-Integrated Query (LINQ)

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.

Visual Basic

Dim classGrades As New System.Collections.Generic.List(Of Integer)(New Integer() {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

More About How to Perform Set Operations

Topic	Location
How to: Combine and Compare String Collections (LINQ)	Language-Integrated Query (LINQ)
How to: Combine and Compare String Collections (LINQ)	Language-Integrated Query (LINQ)
How to: Find the Set Difference Between Two Lists (LINQ)	Language-Integrated Query (LINQ)
How to: Find the Set Difference Between Two Lists (LINQ)	Language-Integrated Query (LINQ)

Concepts

Standard Query Operators Overview

Reference

Distinct Clause (Visual Basic)

System.Linq