c# - EF Code First INSERT 语句与 FOREIGN KEY 约束冲突

Question

当我试图在数据库中插入一条记录时，我得到这个错误信息:

The INSERT statement conflicted with the FOREIGN KEY constraint "FK_dbo.Order_dbo.AspNetUsers_UserId". The conflict occurred in database "Test", table "dbo.AspNetUsers", column 'Id'. The statement has been terminated.

免责声明:我知道之前有人问过这个问题(here、here 和 here)，但没有一个答案能帮助我解决这个错误。

模型如下:

[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; }
}

插入新的 Order 的代码:

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;
}

此行抛出错误:_dbContext.SaveChanges();//这是抛出错误信息的地方。

调试时我可以看到 UserId = userId, 有一个值。

那么为什么我会收到此错误消息？

Answer 1

AspNetUsers数据库中的表必须包含一条记录，其 UserId列具有您使用 userId 设置的值在新秩序中。 Order.UserId不仅是必需的，而且还是 AspNetUsers 的外键表(参见 [ForeignKey("UserId")] 中的 Order 属性)。所以，Order.UserId 还不够有任何 值 (!= null)，它必须有一个对应于 AspNetUsers 中的记录的值表。

异常意味着 AspNetUsers 中不存在这样的记录表。