用修改DataGridView数据并更新数据库

      OleDbDataAdapter dtAdapter;
        private void button15_Click(object sender, EventArgs e)
        {
            string con = "Provider=Microsoft.Jet.OleDb.4.0;Data Source=STUDENT.MDB";
            string sql = "select * from 考生";
            OleDbConnection conn = new OleDbConnection(con);          
            DataTable dt = new DataTable();
            dtAdapter = new OleDbDataAdapter(sql, conn);         
            conn.Open();
            dtAdapter.Fill(dt);
            this.dataGridView1.DataSource = dt;
            conn.Close();
        }

        //将修改数据后的datagridview里数据更新到数据库，要有主键
        private void button17_Click(object sender, EventArgs e)
        {
            try
            {
                DataTable dt = (DataTable)dataGridView1.DataSource;
                OleDbCommandBuilder cmBuilder = new OleDbCommandBuilder(dtAdapter);
                dtAdapter.Update(dt);
            }
            catch (OleDbException exoledb)
            {
                MessageBox.Show(exoledb.Message);

            }
        }