I am not sure of your actual requirement but if it is just to sum values (from selected columns) of every row, you could have used (in Assign activity) datatable.columns("Total Employee Count").Expressions = "ISNULL(Convert(Tier1,System.Int32), 0) + ISNULL(Convert(Tier2, System.Int32), 0) + ISNULL(Convert(Tier3, System.Int32), 0) + ISNULL(Convert(Tier4, System.Int32), 0)"