First I want to say that the better way to do what you need is with the dataset (XSD) object.
You can add one threw the add -> new item... and then chose dataset.
In the past I did it like you do now but it is much easier to manage the tables and their boundings (datagrid, combobox, etc') with the dataset.
Second the code that you look for is this:
SqlCommandBuilder b = new SqlCommandBuilder(_sdataadapter);
After you do all the things you need (add, update , delete) run this and it will update your data base.
usually it is preferred to do those operation separately it works fine together,