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

Definition

Namespace:

System.Collections.Generic

Assembly:

System.Collections.dll

Source:

HashSet.cs

Removes all elements in the specified collection from the current HashSet<T> object.

public:
 virtual void ExceptWith(System::Collections::Generic::IEnumerable<T> ^ other);

public void ExceptWith (System.Collections.Generic.IEnumerable<T> other);

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

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

Parameters

other

IEnumerable<T>

The collection of items to remove from the HashSet<T> object.

Implements

ExceptWith(IEnumerable<T>)

Exceptions

ArgumentNullException

other is null.

Examples

The following example creates two HashSet<T> collections with overlapping sets of data. The lower range of values is then removed from the larger set using the ExceptWith method.

static void Main()
{
    HashSet<int>^ lowNumbers = gcnew HashSet<int>();
    HashSet<int>^ highNumbers = gcnew HashSet<int>();

    for (int i = 0; i < 6; i++)
    {
        lowNumbers->Add(i);
    }

    for (int i = 3; i < 10; i++)
    {
        highNumbers->Add(i);
    }

    Console::Write("lowNumbers contains {0} elements: ", lowNumbers->Count);
    DisplaySet(lowNumbers);

    Console::Write("highNumbers contains {0} elements: ", highNumbers->Count);
    DisplaySet(highNumbers);

    Console::WriteLine("highNumbers ExceptWith lowNumbers...");
    highNumbers->ExceptWith(lowNumbers);

    Console::Write("highNumbers contains {0} elements: ", highNumbers->Count);
    DisplaySet(highNumbers);
}
/* This example provides output similar to the following:
 * lowNumbers contains 6 elements: { 0 1 2 3 4 5 }
 * highNumbers contains 7 elements: { 3 4 5 6 7 8 9 }
 * highNumbers ExceptWith lowNumbers...
 * highNumbers contains 4 elements: { 6 7 8 9 }
 */

HashSet<int> lowNumbers = new HashSet<int>();
HashSet<int> highNumbers = new HashSet<int>();

for (int i = 0; i < 6; i++)
{
    lowNumbers.Add(i);
}

for (int i = 3; i < 10; i++)
{
    highNumbers.Add(i);
}

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

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

Console.WriteLine("highNumbers ExceptWith lowNumbers...");
highNumbers.ExceptWith(lowNumbers);

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

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

/* This example provides output similar to the following:
* lowNumbers contains 6 elements: { 0 1 2 3 4 5 }
* highNumbers contains 7 elements: { 3 4 5 6 7 8 9 }
* highNumbers ExceptWith lowNumbers...
* highNumbers contains 4 elements: { 6 7 8 9 }
*/

let displaySet (set: HashSet<int>) =
    printf "{"

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

    printfn " }"

let lowNumbers = HashSet<int>()
let highNumbers = HashSet<int>()

for i = 0 to 5 do
    lowNumbers.Add i |> ignore

for i = 3 to 9 do
    highNumbers.Add i |> ignore

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

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

printfn "highNumbers ExceptWith lowNumbers..."
highNumbers.ExceptWith(lowNumbers)

printf $"highNumbers contains {highNumbers.Count} elements: "
displaySet highNumbers
// This example provides output similar to the following:
//     lowNumbers contains 6 elements: { 0 1 2 3 4 5 }
//     highNumbers contains 7 elements: { 3 4 5 6 7 8 9 }
//     highNumbers ExceptWith lowNumbers...
//     highNumbers contains 4 elements: { 6 7 8 9 }

Shared Sub Main()

    Dim lowNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()
    Dim highNumbers As HashSet(Of Integer) = New HashSet(Of Integer)()

    For i As Integer = 0 To 5
        lowNumbers.Add(i)
    Next i

    For i As Integer = 3 To 9
        highNumbers.Add(i)
    Next i

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

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

    Console.WriteLine("highNumbers ExceptWith lowNumbers...")
    highNumbers.ExceptWith(lowNumbers)

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

End Sub
' This example provides output similar to the following:
' lowNumbers contains 6 elements: { 0 1 2 3 4 5 }
' highNumbers contains 7 elements: { 3 4 5 6 7 8 9 }
' highNumbers ExceptWith lowNumbers...
' highNumbers contains 4 elements: { 6 7 8 9 }

Remarks

The ExceptWith method is the equivalent of mathematical set subtraction.

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