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HashSet(Of T).UnionWith Method

Modifies the current HashSet(Of T) object to contain all elements that are present in both itself and in the specified collection.

Namespace:  System.Collections.Generic
Assembly:  System.Core (in System.Core.dll)
Syntax

'Declaration

Public Sub UnionWith ( _
	other As IEnumerable(Of T) _
)

Parameters

other
Type: System.Collections.Generic.IEnumerable(Of T)
The collection to compare to the current HashSet(Of T) object.

Implements

ISet(Of T).UnionWith(IEnumerable(Of T))
Exceptions

ExceptionCondition
ArgumentNullException

other is Nothing.

Remarks

This method is an O(n) operation, where n is the number of elements in the other parameter.

Examples

The following example demonstrates how to merge two disparate sets. This example creates two HashSet(Of T) objects, and populates them with even and odd numbers, respectively. A third HashSet(Of T) object is created from the set that contains the even numbers. The example then calls the UnionWith method, which adds the odd number set to the third set.


Imports System
Imports System.Collections.Generic

Class Program

    Shared Sub Main()

        Dim evenNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()
        Dim oddNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()

        For i As Integer = 0 To 4

            ' Populate evenNumbers with only even numbers.
            evenNumbers.Add(i * 2)

            ' Populate oddNumbers with only odd numbers.
            oddNumbers.Add((i * 2) + 1)
        Next i

        Console.Write("evenNumbers contains {0} elements: ", evenNumbers.Count)
        DisplaySet(evenNumbers)

        Console.Write("oddNumbers contains {0} elements: ", oddNumbers.Count)
        DisplaySet(oddNumbers)

        ' Create a new HashSet populated with even numbers.
        Dim numbers As HashSet(Of Integer) = New HashSet(Of Integer)(evenNumbers)
        Console.WriteLine("numbers UnionWith oddNumbers...")
        numbers.UnionWith(oddNumbers)

        Console.Write("numbers contains {0} elements: ", numbers.Count)
        DisplaySet(numbers)
    End Sub


    Private Shared Sub DisplaySet(ByVal coll As HashSet(Of Integer))
        Console.Write("{")
        For Each i As Integer In coll
            Console.Write(" {0}", i)
        Next i
        Console.WriteLine(" }")
    End Sub

End Class
' This example produces output similar to the following:
' evenNumbers contains 5 elements: { 0 2 4 6 8 }
' oddNumbers contains 5 elements: { 1 3 5 7 9 }
' numbers UnionWith oddNumbers...
' numbers contains 10 elements: { 0 2 4 6 8 1 3 5 7 9 }


Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role not supported), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Version Information

.NET Framework

Supported in: 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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