Export (0) Print
Expand All

ValueType.GetHashCode Method

Returns the hash code for this instance.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
Public Overrides Function GetHashCode As Integer

Return Value

Type: System.Int32
A 32-bit signed integer that is the hash code for this instance.

The GetHashCode method applies to types derived from ValueType. One or more fields of the derived type is used to calculate the return value. If you call the derived type's GetHashCode method, the return value is not likely to be suitable for use as a key in a hash table. Additionally, if the value of one or more of those fields changes, the return value might become unsuitable for use as a key in a hash table. In either case, consider writing your own implementation of the GetHashCode method that more closely represents the concept of a hash code for the type.

For more information, see Object.GetHashCode, and System.Collections.Hashtable.

Notes for the Windows Runtime

When you call the GetHashCode method on a Windows Runtime structure, it provides the default behavior for value types that don’t override GetHashCode. This is part of the support that the .NET Framework provides for the Windows Runtime (see .NET Framework Support for Windows Store Apps and Windows Runtime). Windows Runtime structures can’t override GetHashCode, even if they’re written with C# or Visual Basic, because they can’t have methods. (In addition, structures in the Windows Runtime itself don’t inherit ValueType.) However, they appear to have ToString, Equals, and GetHashCode methods when you use them in your C# or Visual Basic code, and the .NET Framework provides the default behavior for these methods.

The following example demonstrates how the GetHashCode method can be overridden by a derived value type.

Public Structure Complex
   Private m_Re As Double 
   Private m_Im As Double 

   Public Overloads Function Equals(ob As Object) As Boolean 
      If TypeOf ob Is Complex Then 
         Dim c As Complex = CType(ob, Complex)
         Return m_Re = c.m_Re And m_Im = c.m_Im
      Else 
         Return False 
      End If 
   End Function 


   Public Overloads Function GetHashCode() As Integer 
      Return m_Re.GetHashCode() ^ m_Im.GetHashCode()
   End Function 

End Structure

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.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

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: 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.

Show:
© 2014 Microsoft