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Set Operations (Visual Basic)

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

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.

Graphic showing the behavior of Distinct().

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.

Graphic showing the action of Except().

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.

Graphic showing the intersection of two 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.

Graphic showing the union of two sequences.

Query Expression Syntax Example

The following example uses the Distinct clause 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