Entity Framework Creates New Record in Table I Didn't Reference when Inserting Into Other Table - sql

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,
};