private void choice(int id)
 {
     DTO_Global.SetGlobalUserId(id);
     if (this.rbHu.Checked == false && this.rbStu.Checked == false)
     {
         MessageBox.Show("You have to choose one");
     }
     else if (this.rbStu.Checked == true)
     {
         MenuStudent mainForm = new MenuStudent();
         this.Hide();
         mainForm.ShowDialog();
         this.Show();
     }
     else
     {
         TeacherMenu form1 = new TeacherMenu();
         form1.Show();
     }
 }
        private void btnLog_Click(object sender, EventArgs e)
        {
            if (this.txtUser.Text == "" || this.txtPass.Text == "")
            {
                MessageBox.Show("Invalid Username or Password", "Login Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else
            {
                DTO_Account DTOacc = new DTO_Account(this.txtUser.Text, this.txtPass.Text);

                if (this.BUSacc.loginAccount(DTOacc))
                {
                    DialogResult dialogResult = MessageBox.Show("Login Successfully");
                    DTO_Global.SetGlobalUserId(BUSUser.getIdByUserName(this.txtUser.Text));
                    //MenuStudent menu1 = new MenuStudent();
                    this.choice(DTO_Global.GlobalUserId);
                }
                else
                {
                    MessageBox.Show("Invalid Username or Password", "Login Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }
        }