实体框架

Question

我正在做MVC 3 Web应用程序并且有很奇怪的问题.这是一些代码:

型号声明:

public class Project
{
    public int ID { get; set; }

    [Required(ErrorMessage = "Write a title.")]
    public string Title { get; set; }

    public DateTime TimeAdded { get; set; }

    [Required(ErrorMessage = "Write some description.")]
    [MaxLength(int.MaxValue)]
    public string Content { get; set; }

    public ICollection<Comment> Comments { get; set; }
}   

public class Comment
{
    public int ID { get; set; }

    [Required()]
    public int ProjectID { get; set; }

    public DateTime TimeAdded { get; set; }

    [Required()]
    public string Text { get; set; }

    public Project project { get; set; }
}

控制器:

public class HomeController : Controller
{
    dataDBContext db = new dataDBContext();

    //
    // GET: /Home

    public ActionResult Index()
    {
        var comments = from c in db.Comments
                       select c;

        var projects = from p in db.Projects
                       orderby p.TimeAdded descending
                       select p;

        return View(projects.ToList());
    }

1. 当我运行项目时,我的视图中看不到注释.
2. 我正在设置一个断点,在linq查询,调试和检查"项目"变量字段注释之后,它们没有被填充.然后我正在检查"评论"变量,它有一些数据.再次检查"项目"变量和SOMEHOW字段填充注释,最后评论显示在网站上.如果我不设置断点并检查是否填充了变量"comments",它们将不会出现在网站上.(我希望这是可以理解的)

3. 我找到了简单的解决方法:

   public ActionResult Index()
   {
       var projects = from p in db.Projects
                      orderby p.TimeAdded descending
                      select p;
   
       foreach (var p in projects)
       {
           var comments = from c in db.Comments
                          where c.ProjectID == p.ID
                          select c;
   
   
           p.Comments = comments.ToList();
       }
   
       return View(projects.ToList());
   }
   

   但它看起来(根据第2点),这可以自动填充SOMEHOW :)

有什么办法吗？

---

另一个尝试基于给定的答案:

public class HomeController : Controller
{
    dataDBContext db;

    public HomeController()
    {
        db = new dataDBContext();
        db.Configuration.LazyLoadingEnabled = false;
    }

    //
    // GET: /Home

    public ActionResult Index()
    {
        var projects = from p in db.Projects
                       orderby p.TimeAdded descending
                       select p;

        return View(projects.ToList());
    }

我有外键.我添加了LazyLoadingEnabled.有project.ToList(),它不起作用.

基于第二个答案,我做了类似的事情:

public class HomeController : Controller
{
    dataDBContext db;

    public HomeController()
    {
        db = new dataDBContext();
    }

    //
    // GET: /Home

    public ActionResult Index()
    {
        var projects = from p in db.Projects
                       orderby p.TimeAdded descending
                       select p;

        var comments = from c in db.Comments
                       select c;

        List<Comment> l = comments.ToList();

        return View(projects.ToList());
    }

我只添加了comments.ToList(),它正在工作.但我不确定这是否是正确的解决方案.可能比我的解决方法更好(第3点).有什么建议？

谢谢

Answer 1

如果您在评论和项目之间有外键,则可以执行以下操作

db.ContextOptions.LazyLoadingEnabled = false;
var projects = from p in db.Projects.Include("Comments")
                       orderby p.TimeAdded descending
                       select p;

当您执行.ToList()时,它将加载所有项目的所有注释.您将能够通过项目对象的导航属性"注释"访问数据.