从MVC Controller类中删除数据库调用的最佳实践

Question

我在ASP.NET MVC Controller类中有一个Action方法,它处理来自相当基本的"创建/编辑用户"页面的表单帖子.我是MVC的新手,所以我一直在关注各种Microsoft教程的代码示例,这是该方法目前的样子:

[AcceptVerbs(HttpVerbs.Post)]
public ViewResult Save([Bind(Prefix = "ServiceUser")]ServiceUser SUser)
{
        if (SUser.ServiceUserId == 0) //new service user
            ServiceUserHelper.AddServiceUser(SUser);
        else //update to existing service user
        {
            using (ProjectDataContext db = DatabaseHelper.CreateContext())
            {
                this.UpdateModel(db.ServiceUsers.Single(su => su.ServiceUserId == SUser.ServiceUserId), "ServiceUser");
                db.SubmitChanges();
            }
        }

        //return a confirmation view
}

这很好用; 但是我的直觉告诉我'ProjectDataContext ...'代码不属于控制器.如果我要将Update功能移动到另一个类(以我使用Insert方法完成的方式),我将失去Controller的UpdateModel()方法的便利性,并且可能最终必须做一些非常详细的事情读取现有实体,更新其属性并提交更改.

所以我的问题是,实现这一目标的最佳方法是什么？LINQ中是否有类似于UpdateModel()的方法可以在提交之前将两个相同类型的实体合并在一起？

谢谢.

Answer 1

大多数人会建议使用"存储库模式"将数据访问代码移出控制器(并使用模拟对象而不是真实数据库进行单元测试).

以下是一些阅读更多的地方:

• 使用Linq到Sql和C#的存储库模式的实现示例
• 专业ASP.NET MVC的第1章(页32)

编辑:

我强烈建议阅读上面链接的整个Scott Guthrie章节.它有很多好的建议.也就是说,这里有一些相关的例子(本章除外)......

首先,我通常喜欢对"更新"与"添加"进行不同的操作.即使它们是用于呈现表单的相同View,通常也可以使用不同的URL来发布编辑和POST新记录.因此,以下是控制器更新操作中使用的存储库模式:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(int id, FormCollection formValues)
{
    //get the current object from the database using the repository class
    Dinner dinner = dinnerRepository.GetDinner(id);
    try
    {
        //update the object with the values submitted
        UpdateModel(dinner);
        //save the changes
        dinnerRepository.Save();
        //redirect the user back to the read-only action for what they just edited
        return RedirectToAction("Details", new { id = dinner.DinnerID });
    }
    catch
    {
        //exception occurred, probably from UpdateModel, so handle the validation errors
        // (read the full chapter to learn what this extention method is)
        ModelState.AddRuleViolations(dinner.GetRuleViolations());
        //render a view that re-shows the form with the validation rules shown
        return View(dinner);
    }
}

这是"添加"示例:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create()
{
    //create a new empty object
    Dinner dinner = new Dinner();
    try
    {
        //populate it with the values submitted
        UpdateModel(dinner);
        //add it to the database
        dinnerRepository.Add(dinner);
        //save the changes
        dinnerRepository.Save();
        //redirect the user back to the read-only action for what they just added
        return RedirectToAction("Details", new { id = dinner.DinnerID });
    }
    catch
    {
        //exception occurred, probably from UpdateModel, so handle the validation errors
        // (read the full chapter to learn what this extention method is)
        ModelState.AddRuleViolations(dinner.GetRuleViolations());
        //render a view that re-shows the form with the validation rules shown
        return View(dinner);
    }
}

对于上面的两个示例,DinnerRepository如下所示:

public class DinnerRepository
{
    private NerdDinnerDataContext db = new NerdDinnerDataContext();
    //
    // Query Methods
    public IQueryable<Dinner> FindAllDinners()
    {
        return db.Dinners;
    }
    public IQueryable<Dinner> FindUpcomingDinners()
    {
        return from dinner in db.Dinners
               where dinner.EventDate > DateTime.Now
               orderby dinner.EventDate
               select dinner;
    }
    public Dinner GetDinner(int id)
    {
        return db.Dinners.SingleOrDefault(d => d.DinnerID == id);
    }
    //
    // Insert/Delete Methods
    public void Add(Dinner dinner)
    {
        db.Dinners.InsertOnSubmit(dinner);
    }
    public void Delete(Dinner dinner)
    {
        db.RSVPs.DeleteAllOnSubmit(dinner.RSVPs);
        db.Dinners.DeleteOnSubmit(dinner);
    }
    //
    // Persistence
    public void Save()
    {
        db.SubmitChanges();
    }
}