Public Class ProductBusinessEntity? 
    Inherits EPS.Business.BusinessObjects.BusinessEntity 

    Public Sub New()
        MyBase.New()
    End Sub

    Public Sub New(ByVal itemId As Guid )
        MyBase.New(itemId)
    End Sub

    Public Overrides Function GetBusinessObject() As EPS.Business.BusinessObjects.IBusinessObject
        Dim oBiz As New ItemBusinessObject 
        Return CType(oBiz, EPS.Business.BusinessObjects.IBusinessObject )
    End Function

    Public Property Name() As String
        Get
            Return Me.GetFieldValue("ProductName").ToString()
        End Get
        Set(ByVal Value As String)
            Me.SetFieldValue("ProductName", Value)
        End Set
    End Property

    Public Property QuantityPerUnit() As String
        Get
            Return Me.GetFieldValue("QuantityPerUnit").ToString()
        End Get
        Set(ByVal Value As String)
            Me.SetFieldValue("QuantityPerUnit", Value)
        End Set
    End Property

    Public ReadOnly Property TheoreticalUnits() As Integer
        Get
            Dim iOne As Integer
            Dim iTwo As Integer
            iOne = CType(Me.GetFieldValue("UnitsInStock"), Integer)
            iTwo = CType(Me.GetFieldValue("UnitsOnOrder"), Integer)
            Return iOne + iTwo
        End Get
    End Property
End Class

Note: Make sure you pay attention to data types. GetFieldValue() for instance deals with variants (objects). However, properties return typed fields. In VB.NET, you can get away without using CType() to convert types if option strict is off. However, all our real-life projects will have option strict on, so you may find yourself re-writing a whole lot of your code (and no, we won't even feel sorry for you... ;-)