EF code The INSERT statement first violated FOREIGN KEY constraints

Question

When I try to insert a record into the database, I get this error message:

The INSERT statement was against the FOREIGN KEY constraint "FK_dbo.Order_dbo.AspNetUsers_UserId". The conflict occurred in the database "Test", the table "dbo.AspNetUsers", the column "Identifier". approval completed.

Disclaimer: I know this question was asked earlier ( here , here and here ), but none of the answers helped me fix this error that I get.

Here are the models:

[Table("Order")]
public class Order
{
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity), Key]
    public int Id { get; set; }

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

    public virtual List<OrderDetails> OrderDetails { get; set; }

    [ForeignKey("UserId")]
    public virtual ApplicationUser User { get; set; }
}    

[Table("OrderDetails")]
public class OrderDetails
{
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity), Key]
    public int Id { get; set; }

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

    [ForeignKey("OrderId")]
    public virtual Order Order { get; set; }
}

public class ApplicationUser : IdentityUser
{
    [MaxLength(15)]
    public string FirstName { get; set; }

    [MaxLength(15)]
    public string LastName { get; set; }

    [MaxLength(50)]
    public string EmailAddress { get; set; }

    public virtual List<Order> Orders { get; set; }
}

Code that inserts a new one Order:

public OrderDetails Add(dynamic addOrderDetails, string userId)
{
    if (addOrderDetails.OrderId == null)
    {
        var order = new Order()
        {
            UserId = userId,
            CreateDate = DateTime.Now,
            Status = OStatus.InProgress,
            Confirmed = (DateTime?)null,
        };

        var newOrder = _dbContext.Orders.Add(order);
        _dbContext.Entry(order).State = EntityState.Added;
        _dbContext.SaveChanges(); // this is where the error msg is being thrown.

        var orderDetails = new OrderDetails()
        {
            OrderId = newOrder.Id,
            ServiceId = addOrderDetails.ServiceId,
            EventStart = start,
            EventEnd = end
        };

        var newOrderDetails = _dbContext.OrderDetails.Add(orderDetails);
        _dbContext.Entry(orderDetails).State = EntityState.Added;
        _dbContext.SaveChanges();
    }

    return null;
}

The error is called on this line: _dbContext.SaveChanges(); // this is where the error msg is being thrown.

When debugging, I see what UserId = userId,matters.

, ?

Answer 1

AspNetUsers , UserId , UserId . Order.UserId , AspNetUsers (. [ForeignKey("UserId")] Order). , , Order.UserId (!= Null), , AspNetUsers.

, AspNetUsers.