HashSet<T>.Clear Method

public:
 virtual void Clear();

public void Clear();

abstract member Clear : unit -> unit
override this.Clear : unit -> unit

Public Sub Clear ()

Implements

Examples

The following example creates and populates a HashSet<T> collection, then clears it and releases the memory referenced by the collection.

HashSet<int> Numbers = new HashSet<int>();

for (int i = 0; i < 10; i++)
{
 Numbers.Add(i);
}

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

Numbers.Clear();
Numbers.TrimExcess();

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

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:
* Numbers contains 10 elements: { 0 1 2 3 4 5 6 7 8 9 }
* Numbers contains 0 elements: { }
*/

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

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

 printfn " }"
// This example produces output similar to the following:
// Numbers contains 10 elements: { 0 1 2 3 4 5 6 7 8 9 }
// Numbers contains 0 elements: { }
let numbers = HashSet<int>()

for i = 0 to 9 do
 numbers.Add i |> ignore

printf $"Numbers contains {numbers.Count} elements: "
displaySet numbers

numbers.Clear()
numbers.TrimExcess()

printf $"Numbers contains {numbers.Count} elements: "
displaySet numbers

Imports System.Collections.Generic

Class Program

 Shared Sub Main()

 Dim Numbers As HashSet(Of Integer) = New HashSet(Of Integer)()

 For i As Integer = 0 To 9
 Numbers.Add(i)
 Next i

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

 Numbers.Clear()
 Numbers.TrimExcess()

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

 End Sub
 ' This code example produces output similar to the following:
 ' Numbers contains 10 elements: { 0 1 2 3 4 5 6 7 8 9 }
 ' Numbers contains 0 elements: { }

 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

Remarks

Count is set to zero and references to other objects from elements of the collection are also released. The capacity remains unchanged until a call to TrimExcess is made.

This method is an O(n) operation, where n is Count.