表适配器填充中未处理的System.NullReferenceException

Question

I keep getting null value expression when the variable sDate does not exist in the data table. It works fine as long as there is a corresponding date in the table. dvtta is the Table Adapter. Here is what I have so far:

            object StartingBal = 0;
            StartingBal = (decimal)dvtta.Balance(acctno, sDate);
            if (StartingBal.GetType() != typeof(DBNull))
            {
                StartingBal = (decimal?)StartingBal;
                StartingBalance = Convert.ToDecimal(StartingBal);
            }
            else
            {
                StartingBalance = 0;
            }

I've been pulling my hair out on this. Any help would be greatly appreciated.

Here is the code for Balance:

 SELECT SUM(AMOUNT) AS Expr1
 FROM     Trans
 WHERE  (ACCT = @account) AND (Date <= @baldate)

Answer 1

Have you tried

if (StartingBal != null) { /* etc. */ }

If it isn't returning anything then aren't you setting your object StartingBal = null. In VB.NET this would be "StartingBal Is Nothing" which worked for me in a very similar situation.