Input string was not in a correct format - sql

Question

I have a class in which i calculate the credit limit left. And return the values through a DataTable. But in the IF condition it is throwing error 'Input string was not in a correct format.', Whats wrong in the code.
Please Help,
Thanks in Advance
string cmd2 = "select sum(FacilityAmountINR),sum(LCAmountPaid) from FacilityIssueDetails where Status='open' AND LCType = 'Inland LC'";
DataTable a = DbRdRw.SqlDbRead(cmd2, "FacilityIssueDetails");
decimal AvailInlandLC = 0;
string totcred = Convert.ToString(a.Rows[0]["Column1"]);
string totpaid = Convert.ToString(a.Rows[0]["Column2"]);
if (totcred != null && totpaid != null)
{
decimal TotalAmountCredit = Convert.ToDecimal(totcred);// error here
decimal TotalAmountpaid = Convert.ToDecimal(totpaid); // error here
AvailInlandLC = InlandLC - TotalAmountCredit + TotalAmountpaid;
}
//*************************************************************************
DataTable AvailableLimitTable = new DataTable();
AvailableLimitTable.Columns.Add("LCType",typeof (string));
AvailableLimitTable.Columns.Add("TotalLimit",typeof (decimal));
AvailableLimitTable.Columns.Add("AvailableLimit",typeof (decimal));
DataRow dr = AvailableLimitTable.NewRow();
dr["LCType"] = "Inland LC";
dr["TotalLimit"] = InlandLC;
dr["AvailableLimit"] = AvailInlandLC;
AvailableLimitTable.Rows.InsertAt(dr, 0);

Answer 1

Try to change the if loop condition if you are getting NULL value from database...
if (totcred != null && totpaid != null && totcred != "Null" && totpaid != "Null" )
{
decimal TotalAmountCredit = Convert.ToDecimal(totcred);// error here
decimal TotalAmountpaid = Convert.ToDecimal(totpaid); // error here
AvailInlandLC = InlandLC - TotalAmountCredit + TotalAmountpaid;
}