VB • Define an Employee Collection Class

Listing 5. Assume that you want to define an employee collection class that implements a custom sorting of the collection. You implement this kind of sort by defining a sorting class that implements the IComparer interface.

Public Class employeeCollection
   Inherits Generic.List(Of employee)


   Enum SortField
     ID
     Name
   End Enum
   Public Shadows Sub Sort(ByVal field _
     As SortField)
     Select Case field
       Case SortField.ID
         MyBase.Sort(New IDComparer)
       Case SortField.Name
         MyBase.Sort(New NameComparer)
     End Select
   End Sub
   Private Class IDComparer
     Implements Generic.IComparer(Of employee)


     Public Function Compare(ByVal x As employee, _
       ByVal y As employee) As Integer _
       Implements System.Collections.Generic. _
       IComparer(Of employee).Compare
       Return x.ID.CompareTo(y.ID)
     End Function
   End Class
   Private Class NameComparer
     Implements Generic.IComparer(Of employee)


     Public Function Compare(ByVal x As employee, _
       ByVal y As employee) As Integer _
       Implements System.Collections.Generic. _
       IComparer(Of employee).Compare
       Return x.Name.CompareTo(y.Name)
     End Function
   End Class
End Class