Object cannot be cast from DBNull to other types....

Question

I have a csv file contains following data: ProdCode, Lender, LoanAmt, APR, Terms, Payment.

I want to store these data into datatable so I defined it like this;

1. define column:
   DataTable dt = new();
   dt.Columns.Add("Term", typeof(int));
   dt.Columns.Add("Payment", typeof(double));
   dt.Columns.Add("Principal", typeof(double));
   dt.Columns.Add("Interest", typeof(double));
   dt.Columns.Add("Balance", typeof(double));
2. add row:
   for (int i = 0; i < Convert.ToInt32(off.Terms) * 12; i++)
   {
   DataRow row = dt.NewRow();
   if (i==0)
   {
   row["Balance"] = Convert.ToDouble(off.LoanAmt);
   }
   row["Term"] = i + 1;
   row["Payment"] = Convert.ToDouble(off.Payment);
   row["Interest"] = Convert.ToDouble(off.APR) / 12 * Convert.ToDouble(row["Balance"]);
   row["Principal"] = Convert.ToDouble(row["Payment"]) - Convert.ToDouble(row["Interest"]);
   row["Balance"] = Convert.ToDouble(row["Balance"]) - Convert.ToDouble(row["Principal"]);
   if(Convert.ToDouble(row["Balance"])<0.0)
   {
   row["Balance"] = 0.0;
   }
   dt.Rows.Add(row);
   }

after running above code, I got an error message:

If somebody pick my fault, I would be very appreciated.

thanks,
c0012

Answer 1

If somebody pick my fault, I would be very appreciated.

That's easy, you assign at the beginning ot the loop row["Balance"] only if i = 0. If i > 0 then row["Balance"] is later DBNull and as the error message already says, you can not convert DBNull to anything.