在 Asp.Net MVC 中将数据插入数据库时如何设置外键值

Question

I am using code first approach. I have two classes as the following:

public class User
{
    [Key]
    [Column(Order = 0)]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int User_id { get; set; }

    [Required]
    [Column(Order = 1)]
    [StringLength(50)]
    [Display(Name = "Name")]
    public string name { get; set; }

    [DataType(DataType.Date)]
    [DisplayFormat(ApplyFormatInEditMode =true,DataFormatString ="{0:dd/MM/yyyy}")]
    public DateTime? date_of_birth { get; set; }

    [Required]
    [Column(Order = 3)]
    [StringLength(254)]
    [Display(Name = "Email")]
    [DataType(DataType.EmailAddress)]
    public string email { get; set; }

    public virtual ICollection<Product> products { get; set; }
}

public class Product
{
    [Key]
    [Required]
    public int product_id { get; set; }

    public int UserId { get; set; }
    public virtual User user { get; set; }

    [Required]
    public string title { get; set; }

    [Required]
    public int type { get; set; }

    [DataType(DataType.Date)]
    public DateTime date_of_release { get; set; }

    [Required]
    public float price { get; set; }
}

I'm trying to add new Product and associate it with the logged user.

This is my view model:

public class AddProductViewModel
{
    [Required]
    public string title { get; set; }

    [Required]
    public int type { get; set; }

    [DataType(DataType.Date)]
    public DateTime date_of_release { get; set; }

    [Required]
    public float price { get; set; }
}

I could not figure out how to set the value of the userId which is the logged in user id so i ended up querying it from the database and setting it as following:

[HttpPost]
public ActionResult AddProduct(AddProductViewModel added)
{
    if(ModelState.IsValid)
    {
        using (KitapTakasDB db = new KitapTakasDB())
        {
            string user_email = User.Identity.GetUserName();

            Product product = new Product();
            product.title = added.title;
            product.price = added.price;
            product.type = added.type ;
            product.userId = db.User.Where(o => o.email == 
            user_email).FirstOrDefault().user_id;

            db.Product.Add(product);
            db.SaveChanges();  //this is where the crash happens...
        }

        return RedirectToAction("Index", "Home");
    }

    return View();
}

When submitting the form, I get an exception on db.SaveChanges() line.

DbUpdateException: 'An error occurred while updating the entries. See the inner exception for details.'

Inner exception:

The conversion of a datetime2 data type to a datetime data type resulted in an out-of-range value

I checked for null DateTime but they were not null.

What is the proper approach of setting the foreign key when adding new entry to the database? And if my approach is correct (I doubt it), how can I fix this error?

Thanks

Answer 1

It seems you forgot to add the date here. Check if it not nullable or add the date:

Product product = new Product();
product.title = added.title;
product.price = added.price;
product.type = added.type ;

product.date_of_release = added.date;

Answer 2

If you have already verified that the date is not null and that is not the problem, you are probably passing a date that is out of bounds between SqlDateTime.MinValue() and SqlDateTime.MaxValue() .

SQL DateMin: (January 1, 1753)

SQL DateMax: (December 31, 9999)