If you ever use the Oracle ODP.Net component with SqlDataSource and get the ORA-01036 Illegal variable name/number error, it is mainly due to the fact that your number of parameters does not match the number in your Insert, Update, or Delete query. I had this problem using a ComposedKey with the ASPxDataGridView from DevExpress. You need to remove the ComposedKey field before executing the query.
Here is the conversation on ASP.Net that helped me resolve this issue.