A Simple Tutorial on Developing ASP.NET Applications in MVC Pattern

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using ASPNetMVCTutorial.Models;

namespace ASPNetMVCTutorial.Controllers
{
    public class StudentsController : Controller
    {
        private StudentsModel GetStudentModelFromSession()
        {
            StudentsModel theModel = (StudentsModel)Session["Students"];
            if (theModel == null)
            {
                theModel = new StudentsModel();
                Session["Students"] = theModel;
            }

            return theModel;
        }

        public ActionResult StudentList()
        {
            StudentsModel theModel = GetStudentModelFromSession();

            ViewData["Students"] = theModel.GetStudents();
            return View();
        }

        public ActionResult AddStudent()
        {
            return View();
        }

        public ActionResult AddStudentAction()
        {
            string Name = Request.Form["textName"];
            string Score = Request.Form["txtScore"];

            if ((Name == null) || (Name.Trim() == ""))
            {
                ViewData["ERROR"] = "Please provide a name for the student to add";
                return View("../Shared/Error");
            }

            if (Name.Length < 6)
            {
                ViewData["ERROR"]
                    = "The student's name should not be less than 6 characters.";
                return View("../Shared/Error");
            }


            int intScore;
            if (!Int32.TryParse(Score, out intScore))
            {
                ViewData["ERROR"]
                    = "Please provide a valid score to the student to add.";
                return View("../Shared/Error");
            }


            if ((intScore < 60) || (intScore > 100))
            {
                ViewData["ERROR"]
                    = "We only accept students with scores between 60 and 100.";
                return View("../Shared/Error");
            }

            StudentsModel theModel = GetStudentModelFromSession();
            theModel.AddStudent(Name, intScore);

            ViewData["Students"] = theModel.GetStudents();
            return View("StudentList");
        }

        public ActionResult DeleteStudent()
        {
            string ID = Request.QueryString["ID"];
            int intID;

            if (!Int32.TryParse(ID, out intID))
            {
                ViewData["ERROR"] = "Please provide a valid student ID";
                return View("../Shared/Error");
            }

            StudentsModel theModel = GetStudentModelFromSession();
            theModel.DeleteStudent(intID);

            return RedirectToAction("StudentList");
        }
    }
}