This documentation is archived and is not being maintained.

HashSet<T>.TrimExcess Method

Sets the capacity of a HashSet<T> object to the actual number of elements it contains, rounded up to a nearby, implementation-specific value.

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

public void TrimExcess()

You can use the TrimExcess method to minimize a HashSet<T> object's memory overhead once it is known that no new elements will be added. To completely clear a HashSet<T> object and release all memory referenced by it, call this method after calling the Clear method.

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

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

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, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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