Get属性返回特定的数据成员

首先我想告诉大家，我已经花了3天时间阅读材料和观看教程，但仍然很难理解这个概念!请帮助我了解一个类的自动实现属性如何决定什么数据成员返回时，你有多个数据成员。下面是一个代码片段，从SQL中提取简单的数据(一个3列的表;Id(int-即PK)、Name(nvarchar)和IsSelected(bit))服务器使用实体框架并生成单选按钮。当您选择每个单选按钮并点击提交时，它会告诉您选择了哪个Department (ID)。

我的问题是，在这个上下文中还有其他2个数据成员，如何自动实现Get方法SelectedDepartment数字取Id字段?

Id SQL服务器中的数据类型是int，但是为SelectedDepartment定义的数据类型是string !它是如何工作的

任何帮助都非常感谢!

模型(Company.cs);

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace RadioButton.Models
{
    public class Company
    {
        public string SelectedDepartment { get; set; }
        public List<Department> Departments
        {
            get
            {
                SampleContext db = new SampleContext();
                return db.Departments.ToList();
            }
        }
    }
}

控制器;

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using RadioButton.Models;
namespace RadioButton.Controllers
{
    public class HomeController : Controller
    {
        private SampleContext db = new SampleContext();
        //
        // GET: /Home/
        [HttpGet]
        public ActionResult Index()
        {
            Company company = new Company();
            return View(company);
        }
        [HttpPost]
        public string Index(Company company)
        {
            if(string.IsNullOrEmpty(company.SelectedDepartment))
            {
                return "You didn't select any";
            }
            else
            {
                return "you have selected " + company.SelectedDepartment;
            }
        }
        //
        // GET: /Home/Details/5
        public ActionResult Details(int id = 0)
        {
            Department department = db.Departments.Find(id);
            if (department == null)
            {
                return HttpNotFound();
            }
            return View(department);
        }
        //
        // GET: /Home/Create
        public ActionResult Create()
        {
            return View();
        }
        //
        // POST: /Home/Create
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create(Department department)
        {
            if (ModelState.IsValid)
            {
                db.Departments.Add(department);
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(department);
        }
        //
        // GET: /Home/Edit/5
        public ActionResult Edit(int id = 0)
        {
            Department department = db.Departments.Find(id);
            if (department == null)
            {
                return HttpNotFound();
            }
            return View(department);
        }
        //
        // POST: /Home/Edit/5
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Edit(Department department)
        {
            if (ModelState.IsValid)
            {
                db.Entry(department).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(department);
        }
        //
        // GET: /Home/Delete/5
        public ActionResult Delete(int id = 0)
        {
            Department department = db.Departments.Find(id);
            if (department == null)
            {
                return HttpNotFound();
            }
            return View(department);
        }
        //
        // POST: /Home/Delete/5
        [HttpPost, ActionName("Delete")]
        [ValidateAntiForgeryToken]
        public ActionResult DeleteConfirmed(int id)
        {
            Department department = db.Departments.Find(id);
            db.Departments.Remove(department);
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        protected override void Dispose(bool disposing)
        {
            db.Dispose();
            base.Dispose(disposing);
        }
    }
}

视图;

@model RadioButton.Models.Company
@{
    ViewBag.Title = "Index";
}
<h2>Index</h2>
@using (Html.BeginForm())
{
    foreach(var department in Model.Departments)
    {
        @Html.RadioButtonFor(m => m.SelectedDepartment, department.Id) @department.Name
    }
    <br />
    <br />
    <input type="submit" value="submit" />
}

private string someProperty;
public string SomeProperty
{
    get { return someProperty; }
    set { someProperty = value; }
}

@Html.RadioButtonFor(m => m.SelectedDepartment, "foo")