private void MainWindow_Load(object sender, EventArgs e)
        {
            user_text_menuitem.Text = "User: "******"Role: Student";
                queryTeacherInformationToolStripMenuItem.Visible = false;
                break;

            case Common.UserType.TEACHER:
                role_text_menuitem.Text = "Role: Teacher";
                submitScoreToolStripMenuItem.Visible = true;
                break;

            case Common.UserType.ADMIN:
                role_text_menuitem.Text                        = "Role: Administrator";
                addAccountToolStripMenuItem.Visible            = true;
                resetUserPasswordToolStripMenuItem.Visible     = true;
                addCourseToolStripMenuItem.Visible             = true;
                addCourseChoosingInfoToolStripMenuItem.Visible = true;
                modifyInformationToolStripMenuItem.Visible     = true;
                break;

            default:
                role_text_menuitem.Text = "Role: Null";
                break;
            }
        }
 public void QueryForLogin()
 {
     using (MySqlConnection connection = SQL_Help.getConnection(Common.UserType.STUDENT))
     {
         connection.Open();
         LoginResult(SQL_Help.ExecuteDataTable("select authority from user_data where username = @name and password = SHA1(@pwd)",
                                               connection, new MySqlParameter[] { new MySqlParameter("@name", username.Text), new MySqlParameter("@pwd", password.Text) }));
         connection.Close();
     }
 }