PartialView or enumerate using foreach in View Model for an inner class using Entity Framework?

Question

I am creating (my first) real simple ASP.NET MVC blog site where I am wondering what is the best approach to sort my comments by the the latest DateTime and how to go about injecting the query results using LINQ into the View or do I need an IQueryable<T> PartialView?

I have been reading up on IEnumerable<T> vs IQueryable<T>, and I would like to think that I wouldn't want the comments in-memory until I have them filtered and sorted.

I was thinking a PartialView using @model Queryable<Models.Blogsite.Comment> where I pass the inner class to the [ChildAction] using the ViewBag or can I just use a foreach loop in the View?

My Article class looks a little like this:

public class Article
{
    //...more properties
    public virtual IQueryable<Comment> Comments { get; set; }
}

My Comment class looks a little like this:

public class Comment
{
    [Key]
    public int CommentId { get; set; }
    [ForeignKey("Article")]
    public int ArticleId { get; set; }
    [DataType(DataType.DateTime), Timestamp,ScaffoldColumn(false)]
    public DateTime Timestamp { get; set; }
    //...more properties
    public virtual Article Article { get; set; }
}

And then if I did implement a PartialView it would look a little like this:

@model IQueryable<BlogSite.Models.Comment>
<table>
    <tbody>
        @foreach (BlogSite.Models.Comment comment in ViewBag.Comments)
        {
            <tr>

                <td>
                      @...

---

I changed my public class Article to this:

public class Article
{
    //...more properties
    public virtual ICollection<Comment> Comments { get; set; }
}

And then I created a method in my ArticleRepository where I call it from UnitOfWOrk which is instantiated within the controller:

public IEnumerable<Comment> GetCommentsByArticleId(int id)
{
    List<Comment> tempList = new List<Comment>();
    var article = GetArticleById(id);
    var comments = article.Comments.Where(c => c.ParentCommentId == null).OrderByDescending(c => c.Timestamp);

    foreach (var c in comments)
    {
        if (c.isRoot)
        {
            tempList.Add(c);

            // Replies
            foreach (var r in article.Comments.Where(x => x.ParentCommentId == c.CommentId).OrderBy(x => x.Timestamp))
            {
                tempList.Add(r);
            }
        }
    }
    return tempList;
}

I have a property called bool isRoot in my comment class so I can render all comments from the property int ParentCommentId so users can respond to these comments. My question now is that if my web application has thousands of articles and the querying is done in-memory and not at the database will this eventually turn into a performance issue?

Won't the temporary list go into garbage collection once it is out of scope? What is the advantage of using IQueryable in this scenario?

Answer 1

Using ViewBag is a bad practice. If you need a sorted list - do it in a controller:

var comments = context.GetComments().ToList();
comments.Sort((x, y) => y.Timestamp.CompareTo(x.Timestamp));
return View(comments)

And pass a sorted list in the view:

@model IEnumerable<BlogSite.Models.Comment>
<table>
  ....