Update DataSet into database!

I´m trying to do a smartdeviceapplication and i have a database and filled the dataset using an adapter.

My problem is that when i change the dataset i can´t update the database using adapter.update().

I believe i have to use oledbcommand but i can´t find it in System.Data namespace.

Is there an alternative to do this update of the dataset to the database or anyone has an idea of what might be happening for me not having that namespace.