I have a datareader that return a lsit of records from a sql server database. I have a field in the database called "Additional". This field is 50% of the time emp
In addition to the suggestions given, you can do this directly from your query like this -
SELECT ISNULL([Additional], -1) AS [Additional]
This way you can write the condition to check whether the field value is < 0 or >= 0.