HashSet<T>.Clear Method

Removes all elements from a HashSet<T> object.

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

public void Clear()



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.

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

static void Main()
    HashSet<int> Numbers = new HashSet<int>();

    for (int i = 0; i < 10; i++)

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


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

/* 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: { }

.NET Framework

Supported in: 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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