Represents a set of values.
Assembly: System.Core (in System.Core.dll)
'Declaration <SerializableAttribute> _ <HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort := True)> _ Public Class HashSet(Of T) _ Implements ISerializable, IDeserializationCallback, ISet(Of T), _ ICollection(Of T), IEnumerable(Of T), IEnumerable
Type Parameters
- T
The type of elements in the hash set.
The HashSet(Of T) class provides high performance set operations. A set is a collection that contains no duplicate elements, and whose elements are in no particular order.
The capacity of a HashSet(Of T) object is the number of elements that the object can hold. A HashSet(Of T) object's capacity automatically increases as elements are added to the object.
Starting with the .NET Framework version 4, the HashSet(Of T) class implements the ISet(Of T) interface.
| Note |
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The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: MayLeakOnAbort. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes. |
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role not supported), 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.Don't bother with
if (!myhash.Contains(item)) { myHash.Add(item); }Just add everything and the HashSet will quickly ignore the duplicates.
http://blogs.msdn.com/bclteam/archive/2006/11/09/introducing-hashset-t-kim-hamilton.aspx
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Yes, but I would only say that only in a general sense. To be deliberately absurd, one could still define an EqualityComparer to use for the HashSet<T> constructor so that duplicates are not considered equal.
Bruce Hamilton
CLR Developer Content
Microsoft
- 5/3/2010
- LukePuplett
- 8/3/2010
- Bruce Hamilton - MSFT
Other collections, such as those that have keys (IDictionary) are case insensitive and so using a HashSet as a filter for a bunch of strings that are to be used as keys will cause key conflicts - possibly random, annoying ones.
- 7/21/2010
- LukePuplett
