GetHashCode on null fields?

Question

How do I deal with null fields in GetHashCode function?

Module Module1   Sub Main()     Dim c As New Contact     Dim hash = c.GetHashCode   End Sub    Public Class Contact : Implements IEquatable(Of Contact)     Public Name As String     Public Address As String      Public Overloads Function Equals(ByVal other As Contact) As Boolean _         Implements System.IEquatable(Of Contact).Equals       Return Name = other.Name AndAlso Address = other.Address     End Function      Public Overrides Function Equals(ByVal obj As Object) As Boolean       If ReferenceEquals(Me, obj) Then Return True        If TypeOf obj Is Contact Then         Return Equals(DirectCast(obj, Contact))       Else         Return False       End If     End Function      Public Overrides Function GetHashCode() As Integer       Return Name.GetHashCode Xor Address.GetHashCode     End Function   End Class End Module 

Answer 1

Typically, you check for null and use 0 for that "part" of the hash code if the field is null:

return (Name == null ? 0 : Name.GetHashCode()) ^    (Address == null ? 0 : Address.GetHashCode()); 

(pardon the C#-ism, not sure of the null check equivalent in VB)