string connectionstring = "Data Source=CE5BC36663C4490\\SQLEXPRESS;Initial Catalog=sql;Integrated Security=True";
        SqlConnection conn = new SqlConnection(connectionstring);
        string str = "select * from dept";
        //SqlCommand cmd = new SqlCommand(str,conn );
        SqlDataAdapter da = new SqlDataAdapter();
        da.TableMappings.Add("Table","dept");
        da.SelectCommand = new SqlCommand(str, conn);
       DataTable  dt = new DataTable ("dept");
       da.Fill(dt );
       
       dt.AcceptChanges();
        dt.Rows [1].Delete ();
      
       
        //dt.RejectChanges();
        //da.Update(dt);
        dt.AcceptChanges();
      
        GridView1.DataSource = dt;
        GridView1.DataBind();

这样做 只是内存 删除，数据库中的数据仍然存在！如何给数据库发请求删除第一行呢