This documentation is archived and is not being maintained.

ValueType.GetHashCode Method

Returns the hash code for this instance.

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

Public Overrides Function GetHashCode As Integer
Dim instance As ValueType
Dim returnValue As Integer

returnValue = instance.GetHashCode
public int GetHashCode ()
public override function GetHashCode () : int
Not applicable.

Return Value

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.

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

End Structure

public class Complex
    public double mRe;
    public double mIm;

    public boolean Equals(Object ob)
        if (ob instanceof Complex) {
            Complex c = (Complex)ob;
            return mRe == c.mRe && mIm == c.mIm;
        else {
            return false;
    } //Equals

    public int GetHashCode()
        return ((System.Double)mRe).GetHashCode() ^ ((System.Double)mIm).
    } //GetHashCode
} //Complex

public class Complex 
    public var m_Re : double;
    public var m_Im : double;

    public override function Equals( ob ) : Boolean{
        if( ob.GetType() == Complex ) {
            var c : Complex = Complex(ob);
            return m_Re==c.m_Re && m_Im==c.m_Im;
        else {
            return false;

    public override function GetHashCode() : int{
        return m_Re.GetHashCode() ^ m_Im.GetHashCode();
            public static function main() {
                   var x : Complex = new Complex();
                   x.m_Re = 1;
                   x.m_Im = 2;
                   var y : Complex = new Complex();
                   y.m_Re = 2;
                   y.m_Im = 1;

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0