/// <summary>
/// Change the top extension for the column to Reference Level
/// </summary>
public void ChangeColumnTopExtension(FamilyInstance column)
{
    AnalyticalModelColumn amc = column.GetAnalyticalModel() as AnalyticalModelColumn;
    if (amc != null)
    {
        using (Transaction tran = new Transaction(column.Document, "Change Top Extension"))
        {
            tran.Start();

            StickElementExtension orgTopExt = amc.TopExtension;
            StickElementExtension newTopExt = StickElementExtension.ReferenceLevel;
            amc.TopExtension = newTopExt;

            TaskDialog.Show("AnalyticalModelColumn", "AnalyticalModelColumn ID: " + amc.Id + "; \nOriginal TopExtension value was: " + orgTopExt + "; \nNew TopExtension value: " + newTopExt);

            tran.Commit();
        }
    }
}

''' <summary>
''' Change the top extension for the column to Reference Level
''' </summary>
Public Sub ChangeColumnTopExtension(column As FamilyInstance)
   Dim amc As AnalyticalModelColumn = TryCast(column.GetAnalyticalModel(), AnalyticalModelColumn)
   If amc IsNot Nothing Then
      Using tran As New Transaction(column.Document, "Change Top Extension")
         tran.Start()

         Dim orgTopExt As StickElementExtension = amc.TopExtension
         Dim newTopExt As StickElementExtension = StickElementExtension.ReferenceLevel
         amc.TopExtension = newTopExt

         TaskDialog.Show("AnalyticalModelColumn", "AnalyticalModelColumn ID: " + amc.Id.ToString + "; " & vbLf & "Original TopExtension value was: " + orgTopExt + "; " & vbLf & "New TopExtension value: " + newTopExt)

         tran.Commit()
      End Using
   End If
End Sub