C# Foreign key Can't add object to list of objects

Question

I have 2 model classes movie and customer. I made a one to many foreign key so that I can add a movie to a list in customer. But now I am unable to add a movie to a customer and I don't get any errors either.

Here is my code.

Movie class

public class Movie
{
    [Key]
    public int MovieId { get; set; }
    public String Name { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime? DateCreated { get; set; }

    public int? CustomerId { get; set; }
    public Customer Customer { get; set; }
}

Customer class

public class Customer
{
    [Key]
    public int CustomerId { get; set; }
    public string Name { get; set; }
    public string LastName { get; set; }
    public bool IsCreated { get; set; }
    public int MaxMovies { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime Created { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime? LastEdited { get; set; }

    [ForeignKey("MovieId")]
    public List<Movie> Movies = new List<Movie>();
}

And here is the code in my CustomerController class that should add the movie to my customer

[HttpGet]
public IActionResult AddMovie(int id)
{
    List<Movie> movieList = new List<Movie>();
    movieList = dbContext.Movies.ToList();

    AddMovieViewModel viewModel = new AddMovieViewModel()
    {
        movies = movieList,
        customer = dbContext.Customers
           .Where(s => s.CustomerId == id)
           .FirstOrDefault()
    };

    return View(viewModel);
}

[HttpPost]
public IActionResult AddMovie (int id,int cid)
{
    Customer customer = dbContext.Customers
        .Where(s => s.CustomerId == cid)
        .FirstOrDefault();
    Movie movie = dbContext.Movies
        .Where(s => s.MovieId == id)
        .FirstOrDefault();
    movie.CustomerId = customer.CustomerId;
    customer.Movies.Add(movie);

    dbContext.SaveChanges();
    return RedirectToAction("Index");
}

I hope someone can tell me whats wrong with my code.

Answer 1

You are not creating new Movie, but searching through existing movies. So create new movie and assign a CustomerId:

Customer customer = dbContext.Customers
    .Where(s => s.CustomerId == cid)
    .FirstOrDefault();
Movie movie = new Movie();
movie.CustomerId = customer.CustomerId;
movie.Name = "My new movie";
movie.DateCreated = DateTime.Now;

dbContext.Customers.Add(customer);
dbContext.Movies.Add(movie);

dbContext.SaveChanges();

EntityFramework will insert a new entity.

Answer 2

I believe this is the model structure you're looking for

Customer

public class Customer
{

    [Key]
    public int CustomerId { get; set; }

    public string Name { get; set; }
    public string LastName { get; set; }
    public bool IsCreated { get; set; }
    public int MaxMovies { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime Created { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime? LastEdited { get; set; }

    public ICollection<Movie> Movies = new List<Movie>();

}

Movie

public class Movie
{

    [Key]
    public int MovieId { get; set; }

    public String Name { get; set; }

    [Column(TypeName = "datetime2")]
    public DateTime? DateCreated { get; set; }

    [ForeignKey("Customer")]
    public int? CustomerId { get; set; }

    public Customer Customer { get; set; }

}

Then when creating/editing a movie, simply assign the movie a CustomerId, you can then retrieve a customer's movies by accessing Customer.Movies