当不需要属性时，引入外键约束可能会导致循环或多个级联路径

Question

我收到此错误：

在表'STCIProductInteractiveInfoes'上引入FOREIGN KEY约束'FK_dbo.STCIProductInteractiveInfoes_dbo.User_ModifyUserID'可能会导致循环或多个级联路径。 指定ON DELETE NO ACTION或ON UPDATE NO ACTION，或修改其他FOREIGN KEY约束。

因此，我在线上（在stackoverflow上）进行了查询，发现这可能是因为需要外键。 我注释掉了必需的属性，但仍然出现此错误。

这是我的课：

namespace PTEManager.Domain
{
    public class PTEInteractiveCourse
    {
        [Key]
        public Guid PTEInteractiveCourseId { get; set; }

        [ScaffoldColumn(false)]
        [Required]
        public DateTime ModifyDate { get; set; }

        [ScaffoldColumn(false)]
        [ForeignKey("ModifyUser")]
        //[Required]
        public int ModifyUserId { get; set; }

        public virtual OpsUser ModifyUser { get; set; }

        [Display(Name = "Package")]
        [Required]
        public int PackageId { get; set; }

        [ScaffoldColumn(false)]
        [Display(Name = "")]
        [Required]
        public int Status { get; set; }

        [Display(Name = "STCI Course")]
        [ForeignKey("STCICourseID")]
        [Required]
        public Guid STCIProductInteractiveInfoID { get; set; }

        public virtual STCIProductInteractiveInfo STCICourseID { get; set; }
    }
}

这是它崩溃的代码：

[HttpGet]
public ActionResult Index()
{
     var model = db.PTEInteractiveCourses
           .Where(p => p.Status == 1)
           .ToList();

     return View(model);
}

当用户删除交互式课程时，不应从用户表中删除该用户。 只是互动课程应该被删除。 在LINQ查询上会发生哪个错误以列出数据，所以我什至不知道要删除它有什么关系，无论如何我们都不会添加删除功能。 好吧，将会有一个删除，但是它所要做的就是向用户隐藏交互过程，但是它将保存数据以防止数据丢失。

我找到了以下代码：

protected override void OnModelCreating( DbModelBuilder modelBuilder )
{
    modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
}

从理论上讲这应该可行，因为我不需要此项目的任何级联删除，但是我将把这些代码放在哪里？ 它在我的datacontext类中说，但是当我这样做时，void关键字上出现构建错误。 这是我的datacontext类：

namespace PTEManager.Domain.Data
{
    public class DataContext : DbContext, IDataContext
    {
        public DataContext()
            : base("HelpDesk")
        {
        }

        //public DataContext(DbConnection existingConnection, bool contextOwnsConnection)
        //    : base(existingConnection, contextOwnsConnection)
        //{
        //}
        /// <summary>
        /// any entity to be persisted must be declared here.
        /// </summary>
        /// 
        public DbSet<OpsUser> OpsUsers { get; set; }

        public DbSet<PTEInteractiveCourse> PTEInteractiveCourses { get; set; }

        public DbSet<PTETrackingClass> PTETrackingClasses { get; set; }

        public DbSet<STCIProductInteractiveInfo> STCIProductInteractiveInfos { get; set; }


    }

}

OpsUser类别：

namespace PTEManager.Domain
{
    [Table("User")]
    public class OpsUser
    {
        [Key]
        public int u_user_id { get; set; }

        public Guid DepartmentID { get; set; }

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

        [MaxLength(30)]
        [Required]
        public string first_nme { get; set; }

        [MaxLength(30)]
        [Required]
        public string last_nme { get; set; }

        [Required]
        public Guid msrepl_tran_version { get; set; }

        [MaxLength(1)]
        [Required]
        public string status { get; set; }

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

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

    }
}

PTETrackingClass：

namespace PTEManager.Domain
{
    public class PTETrackingClass
    {
        [Key]
        public Guid PTETrackingClassId { get; set; }

        [ScaffoldColumn(false)]
        [Required]
        public DateTime ModifyDate { get; set; }


        [ScaffoldColumn(false)]
        [ForeignKey("ModifyUser")]
        [Required]
        public int ModifyUserId { get; set; }

        public virtual OpsUser ModifyUser { get; set; }

        [Display(Name = "Extensions Allowed")]
        [Required]
        public int NumberOfExtensions { get; set; }

        [ScaffoldColumn(false)]
        [Required]
        public int Status { get; set; }

        [Display(Name="Tracking Class Code")]
        [Required]
        public Guid TrackingClassCode { get; set; }

    }
}

STCIProductInteractiveInfo：

namespace PTEManager.Domain
{
    public class STCIProductInteractiveInfo
    {
        [Key]
        public Guid STCIProductInteractiveInfoID { get; set; }

        public Guid MarketingTextID { get; set; }

        [Required]
        public DateTime ModifyDate { get; set; }

        [ForeignKey("ModifyUser")]
        //[Required]
        public int ModifyUserID { get; set; }

        public virtual OpsUser ModifyUser { get; set; }

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

        [MaxLength(100)]
        [Required]
        public string STCICourseName { get; set; }

        public byte STCIProductEmailHTML { get; set; }

        [MaxLength(255)]
        public string STCIProductEmailHTMLDateType { get; set; }

        public int STCIProductEmailHTMLFileLength { get; set; }

        public byte STCIProductEmailText { get; set; }

        [MaxLength(255)]
        public string STCIProductEmailTextDataType { get; set; }
        public string STCIProductEmailTextFileLength { get; set; }

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

        [MaxLength(100)]
        [Required]
        public string STCITrackingClassName { get; set; }

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

    }
}

Answer 1

您的表上有一个循环关系，以解决必须选择的问题：

1）如果用户在STCIProductInteractiveInfo或PTEInteractiveCourse是可选的， STCIProductInteractiveInfo只需更改

public class STCIProductInteractiveInfo // or PTEInteractiveCourse
{
    [Required]
    public int ModifyUserID { get; set; }
}

至

public class STCIProductInteractiveInfo // or PTEInteractiveCourse
{
    // [Required] remove required attribute too
    public int? ModifyUserID { get; set; }
}

2）但是如果您想保留User Required只需在DbContext上添加它即可

public class DataContext : DbContext, IDataContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<STCIProductInteractiveInfo>()
            .HasRequired(e => e.ModifyUser)
            .WithMany()
            .WillCascadeOnDelete(false);
    }
}