Question

In this website, users can register under a username and password, and can also post comments on articles. The models are pretty straightforward:

public class User
{
    public int Id { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
    public bool IsAdmin { get; set; }
    public DateTime JoinDate { get; set; }
    public string AvatarPath { get; set; }
    public string EmailAddress { get; set; }
}

public class ArticleComment
{
    public int Id { get; set; }
    public int ArticleId { get; set; }
    public int UserId { get; set; }
    public string CommenterName { get; set; }
    public string Message { get; set; }
    public DateTime CommentDate { get; set; }
    public User User { get; set; }
}

Entity Framework correctly made the foreign key relationship between UserId on ArticleComment and Id on User when the database was created using code-first.

Here’s my code for when a user posts a new comment:

public JsonResult SubmitComment(int articleId, string comment)
    {
        var response = new JsonResponse();
        var currentUser = _userRepository.GetUserByUsername(User.Identity.Name);

        //...

        var newComment = new ArticleComment
        {
            ArticleId = articleId,
            CommentDate = DateTime.Now,
            CommenterName = currentUser.Username,
            UserId = currentUser.Id,
            User = currentUser,
            Message = comment,
        };

        try
        {
            _articleRepository.Insert(newComment);
        }
        catch (Exception e)
        {
            response.Success = false;
            response.AddError("newComment", "Sorry, we could not add your comment. Server error: " + e.Message);
            return Json(response);
        }

        response.Success = true;
        response.Value = newComment;
        return Json(response);
    }

The values that make up the newComment object all appear to be correct, and the Insert method in my Article repository class is straight and to the point:

    public void Insert(ArticleComment input)
    {
        DataContext.ArticleComments.Add(input);
        DataContext.SaveChanges();
    }

But once this happens, poof: a new record in my Users table appears along with the new record in ArticleComments. All of the info in the new Users record is duplicated from that user’s existing record – the only difference is the value for the primary key Id. What gives?

Answer 1

In addition to my comment, you need to make sure that both _userRepository and _articleRepository are using the same DbContext instance.

Either that, or you can try this:

var newComment = new ArticleComment
{
    ArticleId = articleId,
    CommentDate = DateTime.Now,
    CommenterName = currentUser.Username,
    UserId = currentUser.Id,
    // User = currentUser, let the UserId figure out the User, don't set it yourself.
    Message = comment,
};