HashSet.UnionWith(IEnumerable) Method

public:
 virtual void UnionWith(System::Collections::Generic::IEnumerable ^ other);

public:
 void UnionWith(System::Collections::Generic::IEnumerable ^ other);

public void UnionWith(System.Collections.Generic.IEnumerable other);

abstract member UnionWith : seq<'T> -> unit
override this.UnionWith : seq<'T> -> unit

member this.UnionWith : seq<'T> -> unit

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

Parameters

Implements

Exceptions

Examples

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

HashSet evenNumbers = new HashSet();
HashSet oddNumbers = new HashSet();

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

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

void DisplaySet(HashSet collection)
{
    Console.Write("{");
    foreach (int i in collection)
    {
        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 }
*/

let displaySet (collection: HashSet) =
    printf "{"

    for i in collection do
        printf $" {i}"

    printfn " }"

let evenNumbers = HashSet()
let oddNumbers = HashSet()

for i = 0 to 4 do
    // Populate numbers with just even numbers.
    evenNumbers.Add(i * 2) |> ignore

    // Populate oddNumbers with just odd numbers.
    oddNumbers.Add(i * 2 + 1) |> ignore

printf $"evenNumbers contains {evenNumbers.Count} elements: "
displaySet evenNumbers

printf $"oddNumbers contains {oddNumbers.Count} elements: "
displaySet oddNumbers

// Create a new HashSet populated with even numbers.
let numbers = HashSet evenNumbers
printfn "numbers UnionWith oddNumbers..."
numbers.UnionWith oddNumbers

printf $"numbers contains {numbers.Count} elements: "
displaySet numbers
// 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.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 collection As HashSet(Of Integer))
        Console.Write("{")
        For Each i As Integer In collection
            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.