DataColumn.Expression Question

Hi there,

I have a DataTable which contains 3 columns ,

column[0] = quantity
column[1] = unit_price
column[2] = total

I have set the column[2].Expression equals to quantity * unit_price, then i compute it .


Codes above runs without any problem, i was able to calculate the "total" value and store it in the "total" column

The problem is, i would like to sum up the column "total" of the datatable , for instance : the datatable has 3 products, then i want to calculate the sum of the "total" columns. Normally , this could be done using the same code :



but the "total" column's expression has been changed to "quantity*unit_price" previously....hence "Sum(total)" won't work.

I try to assign the "total" column expression back to "total" , but it returns
the Exception:



Anyone knows how to solve this ? thanks a lot