Question

I’m trying to make a simple forum using MVC and I can’t figure out why the user that is posting the reply is getting duplicated.

Here is the Reply Action:

[HttpPost]
public ActionResult Reply(string Title, string Content,int ReplyTo)
{
    Post masterPost = db.Posts.FirstOrDefault(p => p.PostID == ReplyTo);
    Post post = new Post();
    post.PostID = 0;
    post.CreatedOn = DateTime.Now;
    post.ModifiedOn = DateTime.Now;
    post.ReplyTo = masterPost;
    post.Forum = db.Forums.FirstOrDefault(f=>f.ForumID == masterPost.Forum.ForumID);
    post.User = (User)Session["User"];
    post.Title = Title;
    post.Content = Content;

    //if (ModelState.IsValid)
    //{
        db.Posts.Add(post);
        db.SaveChanges();
        return RedirectToAction("View", "Posts", new { id = ReplyTo });
    //}
    return View(post);
}

This is the Post entity:

public class Post
{
    [Key]
    public int PostID { get; set; }
    public string Title { get; set; }
    [DataType(DataType.MultilineText)]
    public string Content { get; set; }
    public DateTime CreatedOn { get; set; }
    public DateTime? ModifiedOn { get; set; }
    public virtual Forum Forum { get; set; }
    public virtual User User { get; set; }
    public virtual Post ReplyTo { get; set; }
}

This is the User entity:

public class User
{
    public int UserID { get; set; }
    public string Name { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
    public string Email { get; set; }
    public DateTime RegisteredOn { get; set; }
}

Whenever the ReplyTo action is called it creates the Post but it also duplicates the User that is stored in the session (with a different UserID).

What am I doing wrong?

Answer 1

Even though you don’t state it, it looks like you use Entity Framework.

If so, the culprit is probably this line

post.User = (User)Session["User"];

The “User” you store in session is now disconnected from Entity Framework, so EF assumes it is a brand-new user.

There are several ways to solve this. The one I prefer is to also add a UserId property to your Post class and use that

public class Post
{
    // Stuff
    public virtual int UserId { get; set; }
}

Then do:

post.UserId = ((User)Session["User"]).Id;

Entity Framework uses a convention to understand that you want to link that user to that post.