difference between dataset.acceptchanges() and dataadapter.update() in .net

AcceptChanges only updates your rows in the (in memory) dataset, that is - marks them as "not needed for actual database update". If you want to update your rows to the database, call your tableadapter's Update method. This method will call AcceptChanges on your rows if the rows get successfully updated to the database. The point here is, you should only call AcceptChanges on your rows, if you don't want them to be sent to your database to update records.