HashSet<T>.UnionWith(IEnumerable<T>) HashSet<T>.UnionWith(IEnumerable<T>) HashSet<T>.UnionWith(IEnumerable<T>) HashSet<T>.UnionWith(IEnumerable<T>) Method

Definition

Modifies the current HashSet<T> object to contain all elements that are present in itself, the specified collection, or both.

public:
 virtual void UnionWith(System::Collections::Generic::IEnumerable<T> ^ other);
public void UnionWith (System.Collections.Generic.IEnumerable<T> other);
abstract member UnionWith : seq<'T> -> unit
override this.UnionWith : seq<'T> -> unit
Public Sub UnionWith (other As IEnumerable(Of T))
Parameters
other
IEnumerable<T> IEnumerable<T> IEnumerable<T> IEnumerable<T>

The collection to compare to the current HashSet<T> object.

Exceptions

Examples

The following example demonstrates how to merge two disparate sets. This example creates two HashSet<T> objects, and populates them with even and odd numbers, respectively. A third HashSet<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.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        HashSet<int> evenNumbers = new HashSet<int>();
        HashSet<int> oddNumbers = new HashSet<int>();

        for (int i = 0; i < 5; i++)
        {
            // Populate numbers with just even numbers.
            evenNumbers.Add(i * 2);

            // Populate oddNumbers with just odd numbers.
            oddNumbers.Add((i * 2) + 1);
        }

        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.
        HashSet<int> numbers = new HashSet<int>(evenNumbers);
        Console.WriteLine("numbers UnionWith oddNumbers...");
        numbers.UnionWith(oddNumbers);

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

    }

    private static void DisplaySet(HashSet<int> set)
    {
        Console.Write("{");
        foreach (int i in set)
        {
            Console.Write(" {0}", i);
        }
        Console.WriteLine(" }");
    }
}
/* 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 }
 */
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 }

Remarks

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

Applies to