ASP.NET MVC和Mongodb参考

Question

I have problem with my application. In my simple blog application I have Post and Category collection: Post.cs

public class Post 
{
    [ScaffoldColumn(false)]
    [BsonId]
    public ObjectId PostId { get; set; }

    [ScaffoldColumn(false)]
    [BsonDateTimeOptions(Kind = DateTimeKind.Local)]
    public DateTime Date { get; set; }

    [Required]
    public string Title { get; set; }

    [ScaffoldColumn(false)]
    public string Url { get; set; }

    public ObjectId CategoryId { get; set; }

    [UIHint("WYSIWYG")]
    [AllowHtml]
    public string Details { get; set; }

    [ScaffoldColumn(false)]
    public string Author { get; set; }

    [ScaffoldColumn(false)]
    public int TotalComments { get; set; }

    [ScaffoldColumn(false)]
    public IList<Comment> Comments { get; set; }
}

and category.cs

 public class Category
{
    [ScaffoldColumn(false)]
    [BsonId]
    public ObjectId CategoryId { get; set; }

    [ScaffoldColumn(true)]
    [Required]
    public string Name { get; set; }

}

PostControler:

 [HttpPost]
    public ActionResult Create(Post post)
    {

        if (ModelState.IsValid)
        {
            post.Url = post.Title.GenerateSlug();
            post.Author = User.Identity.Name;
            post.Date = DateTime.Now;
            post.CategoryId = 
            _postService.Create(post);
            return RedirectToAction("Index");
        }

        return View();
    }

When I create new post, I want to choose category from list and save "_id" of category in post collection. I don't have any idea to resolve this. Can anybody give some suggestions, to solve this.

Answer 1

I don't really understand the problem here, but let's walk through this step-by-step:

First, you'll have to populate the list of available categories, so you'll have to call FindAll on your Category collection.

Second, you will need to pass this list to the frontend, so you need a view model class that contains some kind of dictionary so you can bind this to a dropdown ( <select> ), for instance, ie

class PostCreateViewModel
{
     Dictionary<string, string> Categories {get; set;}
     /// ...
}

[HttpGet]
public ActionResult Create()
{
  var categories = _categoryService.All();
  var vm = new PostCreateViewModel();
  vm.Categories = categories.ToDictionary(p => p.CategoryId.ToString());
  // etc.
  return View(vm);
}

Third, your Post handler should verify that the CategoryId is correct:

[HttpGet]
public ActionResult Create(Post post)
{
  // Make sure the given category exists. It would be better to have a 
  // PostService with a Create action that checks this internally, e.g.
  // when you add an API or a different controller creates new posts as
  // a side effect, you don't want to copy that logic.
  var category = _categoryService.SingleById(post.CategoryId);
  if(category == null)
      throw new Exception("Invalid Category!");

  // Insert your post in the DB

  // Observe the PRG pattern: Successful POSTs should always redirect:
  return Redirect("foo"); 
}

Some details can be tricky, for instance I'm assuming that post.CategoryId will be populated through a model binder, but you might have to write a custom model binder for ObjectId or use a ViewModel class with a string and parse the string using ObjectId.Parse . In general, I'd suggest using ViewModels everywhere and use the help of something like AutoMapper to avoid writing tons of boilerplate copy code.