ASP.NE - Selecting an item from a dropdown listbox control

Question

I have a dropdown listbox whose SQLDataSource connects to an Oracle database from a SQL Server 2005.  Based on the department selection, the query should display all the employees in the selected department.  However, it only list a null value.  The SQL @parameter is not recognized by Oracle but the equivalent search criteria is:
Select * from department
Where department_name LIKE :department_name.
Any help would be greatly appreciated.