ValueType.GetHashCode Method
Returns the hash code for this instance.
[Visual Basic] Overrides Public Function GetHashCode() As Integer [C#] public override int GetHashCode(); [C++] public: int GetHashCode(); [JScript] public override function GetHashCode() : int;
Return Value
A 32-bit signed integer that is the hash code for this instance.
Remarks
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 one or more of those fields contains a mutable value, the return value might be unpredictable, and unsuitable for use as a key in a hash table. In that case, consider writing your own implementation of GetHashCode that more closely represents the concept of a hash code for the type.
For more information, see Object.GetHashCode, and System.Collections.Hashtable.
Example
The following example demonstrates how the GetHashCode method can be overridden by a derived value type.
[Visual Basic] 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 [C#] public struct Complex { public double m_Re; public double m_Im; public override bool Equals( object ob ){ if( ob is Complex ) { Complex c = (Complex) ob; return m_Re==c.m_Re && m_Im==c.m_Im; } else { return false; } } public override int GetHashCode(){ return m_Re.GetHashCode() ^ m_Im.GetHashCode(); } } [C++] public __gc struct Complex { double m_Re; double m_Im; bool Equals(Object* ob) { if (dynamic_cast<Complex*>(ob)) { Complex* c = dynamic_cast<Complex*>(ob); return m_Re==c->m_Re && m_Im==c->m_Im; } else { return false; } } int GetHashCode() { return __box(m_Re)->GetHashCode() ^ __box(m_Im)->GetHashCode(); } }; [JScript] 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; Console.Write(x.Equals(y)); } }
Requirements
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard