asp.net mvc 三层架构的增删改查

以下是ASP.NET MVC三层架构的增删改查操作的示例代码：

1. Model层代码：

public class User
{
    public int ID { get; set; }
    public string Name { get; set; }
    public string Title { get; set; }
}

2. DataAccess层代码：

public class UserDataAccess
{
    public List<User> GetAllUsers()
    {
        using (var context = new UserContext())
        {
            return context.Users.ToList();
        }
    }

    public User GetUserById(int id)
    {
        using (var context = new UserContext())
        {
            return context.Users.FirstOrDefault(u => u.ID == id);
        }
    }

    public void AddUser(User user)
    {
        using (var context = new UserContext())
        {
            context.Users.Add(user);
            context.SaveChanges();
        }
    }

    public void UpdateUser(User user)
    {
        using (var context = new UserContext())
        {
            var oldUser = context.Users.FirstOrDefault(u => u.ID == user.ID);
            if (oldUser != null)
            {
                oldUser.Name = user.Name;
                oldUser.Title = user.Title;
                context.SaveChanges();
            }
        }
    }

    public void DeleteUser(int id)
    {
        using (var context = new UserContext())
        {
            var user = context.Users.FirstOrDefault(u => u.ID == id);
            if (user != null)
            {
                context.Users.Remove(user);
                context.SaveChanges();
            }
        }
    }
}

3. Service层代码：

public class UserService
{
    private readonly UserDataAccess _userDataAccess;

    public UserService()
    {
        _userDataAccess = new UserDataAccess();
    }

    public List<User> GetAllUsers()
    {
        return _userDataAccess.GetAllUsers();
    }

    public User GetUserById(int id)
    {
        return _userDataAccess.GetUserById(id);
    }

    public void AddUser(User user)
    {
        _userDataAccess.AddUser(user);
    }

    public void UpdateUser(User user)
    {
        _userDataAccess.UpdateUser(user);
    }

    public void DeleteUser(int id)
    {
        _userDataAccess.DeleteUser(id);
    }
}

4. Controller层代码：

public class UserController : Controller
{
    private readonly UserService _userService;

    public UserController()
    {
        _userService = new UserService();
    }

    public ActionResult Index()
    {
        var users = _userService.GetAllUsers();
        return View(users);
    }

    public ActionResult Details(int id)
    {
        var user = _userService.GetUserById(id);
        return View(user);
    }

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

    [HttpPost]
    public ActionResult Create(User user)
    {
        if (ModelState.IsValid)
        {
            _userService.AddUser(user);
            return RedirectToAction("Index");
        }
        return View(user);
    }

    public ActionResult Edit(int id)
    {
        var user = _userService.GetUserById(id);
        return View(user);
    }

    [HttpPost]
    public ActionResult Edit(User user)
    {
        if (ModelState.IsValid)
        {
            _userService.UpdateUser(user);
            return RedirectToAction("Index");
        }
        return View(user);
    }

    public ActionResult Delete(int id)
    {
        var user = _userService.GetUserById(id);
        return View(user);
    }

    [HttpPost, ActionName("Delete")]
    public ActionResult DeleteConfirmed(int id)
    {
        _userService.DeleteUser(id);
        return RedirectToAction("Index");
    }
}

以上代码实现了对User表的增删改查操作，其中Model层定义了User实体类，DataAccess层实现了对User表的增删改查操作，Service层对DataAccess层进行了封装，Controller层实现了对应的Action方法，用于响应用户的请求。