Queryable.Distinct(Of TSource) Method (IQueryable(Of TSource))

 
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Returns distinct elements from a sequence by using the default equality comparer to compare values.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

<ExtensionAttribute>
Public Shared Function Distinct(Of TSource) (
	source As IQueryable(Of TSource)
) As IQueryable(Of TSource)

Parameters

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

The IQueryable(Of T) to remove duplicates from.

Return Value

Type: System.Linq.IQueryable(Of TSource)

An IQueryable(Of T) that contains distinct elements from source.

Type Parameters

TSource

The type of the elements of source.

Exception Condition
ArgumentNullException

source is null.

The Distinct(Of TSource)(IQueryable(Of TSource)) method generates a MethodCallExpression that represents calling Distinct(Of TSource)(IQueryable(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 the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Distinct(Of TSource)(IQueryable(Of TSource)) depends on the implementation of the type of the source parameter. The expected behavior is that it returns an unordered sequence of the unique items in source.

The following code example demonstrates how to use Distinct(Of TSource)(IQueryable(Of TSource)) to return distinct elements from a sequence.

Dim ages As List(Of Integer) = New List(Of Integer)(New Integer() {21, 46, 46, 55, 17, 21, 55, 55})

Dim distinctAges As IEnumerable(Of Integer) = ages.AsQueryable().Distinct()

Dim output As New System.Text.StringBuilder
output.AppendLine("Distinct ages:")

For Each age As Integer In distinctAges
    output.AppendLine(age)
Next

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

' This code produces the following output:
'
' Distinct(ages)
' 21
' 46
' 55
' 17

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1
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