Multiplying columns in a datatable

Question

I have a datatable in C# with a "price" column and an "allocation" column, and I need to multiply the price column by the allocation column and put the result in the price column. Is there a way to do with without looping over the table? I have tried something like this:

DataTable dt = getData();
dt.Columns["Price"].Expression = "Allocation * Price";

But obviously this gives me the following exception:

Cannot set Expression property due to circular reference in the expression.

Does anyone know of another way to accomplish this? Thanks beforehand.

Answer 1

You could use a LINQ expression to do it in one line:

dt.Rows.ForEach(x => x["Price"] = (double)x["Price"] * (double)x["Allocation"]);

Answer 2

You could just add another column to the DataTable:

dt.Columns.Add("TotalPrice", typeof(decimal));
dt["TotalPrice"] = "Allocation * Price";

Answer 3

Add a new column whose value is calculated from the other two:

dt.Columns.Add("TotalPrice", typeof(decimal), "Allocation * Price");

With this approach, the TotalPrice will always be up to date if you change the Price or Allocation