When customizing a field in BO mapper to use “Return Alternate on Null / Set Null on Alternate” either by val or ref, the closing ‘EndIF’ is missing in the designer code generated for the Set portion of the public property. 
 
Example:
 
BusinessFieldDisplayInEditor(), _
     Description("Default action taken by user"), _
     DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)> _
    Public Property [ap_DefaultAddedTask]() As System.Int32
        Get
            Dim loValue As Object
            loValue = Me.CurrentRow.Item("ap_DefaultAddedTask")
            If loValue Is DBNull.Value Then
                Return 0
            Else
                Return CType(loValue, System.Int32)
            End If
        End Get
        Set(ByVal value As System.Int32)
            If value <> 0 Then
                Me.CurrentRow.Item("ap_DefaultAddedTask") = value
            Else
  à            Me.CurrentRow.Item("ap_DefaultAddedTask") = DBNull.Value
        End Set
    End Property
 
-Larry