DataTable修改后，如何更新数据库

private void Form1_Load(object sender, EventArgs e)
 {
 string sqlConnectionString = "Data Source=ComputerName-PC;Initial Catalog=charge_sys;User ID=sa;PWD=123456;";
 SqlConnection sqlConnection = new SqlConnection(sqlConnectionString);//初始化sqlconnection

 DataTable table = new DataTable();
 SqlDataAdapter sqlAdap = new SqlDataAdapter("select * from testB ", sqlConnection);

 sqlConnection.Open();
 sqlAdap.Fill(table);
 sqlConnection.Close();

 //将testB表中的数据显示在dataGridView中
 this.dataGridView1.DataSource = table;

 }

private void butUpdate_Click(object sender, EventArgs e)
 {
 DataTable table = new DataTable();
 table = (DataTable)this.dataGridView1.DataSource;

 string sqlConnectionString = "Data Source=WangHaitao-PC;Initial Catalog=charge_sys;User ID=sa;PWD=123456;";
 SqlConnection sqlConnection = new SqlConnection(sqlConnectionString);
 
 SqlCommand sqlCommand = new SqlCommand("select * from testB", sqlConnection);
 
 SqlDataAdapter sqlAdap = new SqlDataAdapter(sqlCommand);
 SqlCommandBuilder sqlBuilder = new SqlCommandBuilder(sqlAdap);//必须有

 sqlConnection.Open();
 sqlAdap.Fill(table);

 //testB表中必须存在主键，否则无法更新
 sqlAdap.Update(table);

 sqlConnection.Close();
 MessageBox.Show("aa");

 }