Object-oriented Printing with Inka, Part 1

Namespace Aggregates
    Public Class Sum
        Implements Core.IAggregateFunction

        Private _sum As Double = 0

        Public Sub Current(ByVal ParamArray args() As Object) Implements Core.IAggregateFunction.Current
            DesignByContract.Check.Require(args.Length = 1, "The Sum aggregate accepts only one argument")
            _sum += CDbl(args(0))
        End Sub

        Public ReadOnly Property Value() As String Implements Core.IAggregateFunction.Value
            Get
                Return _sum
            End Get

        End Property

    End Class
End Namespace