ExecuteScalar returns null or DBNull (development or production server)

Question

I\'m trying to add a column to an existing DataRow in C#. Afterwards the column will be filled with a single value from my database.

DataRow dr already

Answer 1

Use the ISNULL() function in your SQL.

ISNULL ( check_expression , replacement_value )

ie...

SELECT ISNULL(SUM(Price),0) FROM Order

Answer 2

ExecuteScalar returns DBNull for null value from query and null for no result. Maybe on your development server it never occured (null result from query).

Answer 3

Clearly in production you have either a NULL returned from the command execution or something different in the connectionstring or whatever; as a general rule you should always test for DBNull before casting/converting directly to another type the result of ExecuteScalar.

Check Rein's answer here (and vote him up) for his nice suggested solution:

Unable to cast object of type 'System.DBNull' to type 'System.String`