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

I received this error:

Introducing FOREIGN KEY constraint 'FK_dbo.STCIProductInteractiveInfoes_dbo.User_ModifyUserID' on table 'STCIProductInteractiveInfoes' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

So I looked it up online (on stackoverflow) and I see that it can be because the foreign key is required. I commented out the required property and I am still getting this error.

Here is my class:

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; }
    }
}

and here is the code that it is crashing on:

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

     return View(model);
}

When a user deletes an Interactive Course, a user should not be deleted from the user table; just the interactive course should be deleted. Which this error is happening on a LINQ query to list the data so I do not even know what deleting it would have to do with it, we will not be adding a delete function anyway. Well there will be a delete but all it will do is hide the interactive course from the user but it will save the data to prevent data loss.

I have found this code:

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

which should theoretically work because I do not need any cascading deletes for this project but where would I put this code? It says in my datacontext class but when I do I have a build error on the void keyword. Here is my datacontext class:

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 Class:

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

You have a circular relation on your Tables to resolve you have to option:

1) If User is optional in STCIProductInteractiveInfo or PTEInteractiveCourse you could simply change

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

to

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

2) But if you want keep User Required simply add this on your DbContext

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