下面是我写的语句，为什么执行后数据表没有变化？MessageBox.Show(rowsAffected.ToString());显示的数据明明是表的记录数？是不是数据库设置问题？
请高手指点！



using (SqlConnection sqlConnection1 = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=|DataDirectory|\\myDate.mdf;Integrated Security=True;User Instance=True"))
                {

                    Int32 rowsAffected;
                    string queryString = null;
                    SqlCommand command = new SqlCommand();

                    sqlConnection1.Open();
                    command.Connection = sqlConnection1;
                    command.CommandType = CommandType.Text;

                    queryString = "delete  from City";
                    command.CommandText = queryString;
                    rowsAffected = command.ExecuteNonQuery();
                    sqlConnection1.Close();
                    MessageBox.Show(rowsAffected.ToString());

                }