Handle NULL values when reading through OracleDataReader?

Question

I'm working on my first ASP.Net application, and seem to be hitting a lot of hurdles (background primarily in WinForms with a recent MVC5 project under my belt).

I am successfully making my DB connection using OracleCommand and executing my query, but when I try reading through the rows I am getting a Column contains NULL value on the second row for odr.GetDecimal(1). Anyone know how to handle null values when reading through an OracleDataReader?

Below is my code:

        List<YearsOfService> yearsOfService = new List<YearsOfService>();
        string SQL = "SELECT SCHOOL_YEAR as YEAR, " +
                            "TOTAL_SERVICE_CREDIT as ServiceCredited, " +
                            "RETIREMENT_SALARY as Salary, " +
                            "SOURCE_VALUE as CoveredEmployer " +
                     "FROM " + Schema + ".RANDOM_ORACLE_TABLE a " +
                     "WHERE MEMBER_ACCOUNT_ID = :memberAccountId";

        DbConnection dbc = new DbConnection();
        OracleCommand cmd = dbc.GetCommand(SQL);
        cmd.Parameters.Add(new OracleParameter("memberAccountId", memberAccountId));
        OracleDataReader odr = cmd.ExecuteReader();

        int counter = 0;
        if (odr.HasRows)
        {
            while (odr.Read())
            {
                YearsOfService yos = new YearsOfService();
                yos.Year = odr.GetInt16(0);
                yos.ServiceCredited = odr.GetDecimal(1); // Error on Second Pass

                yos.Salary = odr.GetDecimal(2);

                yos.CoveredEmployer = odr.GetString(3);

                yearsOfService.Add(yos);
                counter++;
            }
        }

        return yearsOfService;
    }

I had thought a simple check for NULL and if so replace with 0 (since expecting a Decimal value) would work with the following, but no luck. Same error: yos.ServiceCredited = Convert.IsDBNull(odr.GetDecimal(1)) ? 0 : odr.GetDecimal(1);.

Full error is:

An exception of type 'System.InvalidCastException' occurred in Oracle.DataAccess.dll but was not handled in user code

Additional information: Column contains NULL data

I have confirmed that my 2 rows being returned are in the following format:

Year|CreditedService|Salary  |CoveredEmployer
2013|0.70128        |34949.66|ER
2014|NULL           | 2213.99|NULL

Anyone have advice on how best to proceed? How should I handle receiving the NULL value when reading through my OracleDataReader?

Answer 1

yos.ServiceCredited = odr.IsDBNull(1) ? 0 : odr.GetDecimal(1);

OracleDataReader provides a IsDBNull() method.

And the docs on GetDecimal() ask us to do this

Call IsDBNull to check for null values before calling this method.