Cycles and Multiple cascade Paths using EF Code First

Question

I'm getting so confused!!! This is my first time using MVC3 and EF Code First. I'm getting the following error:

Introducing FOREIGN KEY constraint 'FK_dbo.CityUsers_dbo.Cities_CityID' on table 'CityUsers' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints. Could not create constraint.

I have been working on it for hours and done whatever I could but just unable to handle that!

The Scenario is that, there is a Man class from which the User is derived. Every user belongs to only ONE City. By user I mean admin users. Each of them can Insert/Update several Cities and each City can be modified by only one User at a time. I have created a third table named 'CityUser' to track users who modify City records.

Here is my model classes:

public class Man
{
    [Key]
    [DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
    public long ID { get; set; }
    //------------------------------------------------------------//
    [Required, MaxLength(20)]
    [LocalizedAttribute("FName")]
    public string FName { get; set; }
    //------------------------------------------------------------//
    [Required, MaxLength(20)]
    [LocalizedAttribute("LastName")]
    public string LastName { get; set; }
    //------------------------------------------------------------//
    [Required]
    [RegularExpression("^[0-9]+$", ErrorMessageResourceName = "ErrorOnlyNumbers", ErrorMessageResourceType = typeof(MAHAL_E_MA_Model.Properties.Resources))]
    [LocalizedAttribute("Mobile")]
    public string Mobile { get; set; }
    //------------------------------------------------------------//
    [LocalizedAttribute("Phone")]
    [RegularExpression("^[0-9]+$", ErrorMessageResourceName = "ErrorOnlyNumbers", ErrorMessageResourceType = typeof(MAHAL_E_MA_Model.Properties.Resources))]
    public string HomePhone { get; set; }
    //------------------------------------------------------------//
    [RegularExpression("^[0-9]+$")]
    [LocalizedAttribute("IDCardNumber")]
    public string IDCardNumber { get; set; }
    //------------------------------------------------------------//
    [RegularExpression("^[0-9]+$")]
    [LocalizedAttribute("NationalCode")]
    public string NationalCode { get; set; }
    //------------------------------------------------------------//
    [MaxLength(10)]
    [LocalizedAttribute("DOB")]
    public int DOB { get; set; }
    //------------------------------------------------------------//
    [Required]
    public int CityID { get; set; }
    [ForeignKey("CityID")]
    public virtual City CityParent { get; set; }
    //------------------------------------------------------------//
    [MaxLength(100)]
    [LocalizedAttribute("Address")]
    public string Address { get; set; }
    //------------------------------------------------------------//
    [LocalizedAttribute("PostalCode")]
    public string PostalCode { get; set; }
    //------------------------------------------------------------//
    [MaxLength(255)]
    [LocalizedAttribute("PhotoPath")]
    public string PhotoPath { get; set; }
}

 public class User : Man
{
    [MaxLength(20)]
    [LocalizedAttribute("Username")]
    public string UserName { get; set; }
    //------------------------------------------------------------//
    [DataType(DataType.Password)]
    [MaxLength(100), MinLength(6, ErrorMessageResourceType = typeof(MAHAL_E_MA_Model.Properties.Resources), ErrorMessageResourceName = "ErrorPasswordLength")]
    [LocalizedAttribute("Password")]
    public string Password { get; set; }
    //------------------------------------------------------------//
    [DataType(DataType.Password)]
    [Compare("Password", ErrorMessageResourceType = typeof(MAHAL_E_MA_Model.Properties.Resources), ErrorMessageResourceName = "ErrorConfirmPassword")]
    [LocalizedAttribute("ConfirmPassword")]
    public string ConfirmPassword { get; set; }
    //------------------------------------------------------------//
    [DataType(DataType.EmailAddress, ErrorMessageResourceType = typeof(MAHAL_E_MA_Model.Properties.Resources), ErrorMessageResourceName = "ErrorEmailInvalid")]
    [MaxLength(20)]
    [RegularExpression(@"[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}")]
    [LocalizedAttribute("Email")]
    public string Email { get; set; }
    //------------------------------------------------------------//
    [MaxLength(30)]
    [LocalizedAttribute("Title")]
    public string Title { get; set; }
    //------------------------------------------------------------//
    [MaxLength(10)]
    [LocalizedAttribute("HireDate")]
    public int HireDate { get; set; }
    //------------------------------------------------------------//
    [LocalizedAttribute("ReportsTo")]
    public long ReportsTo { get; set; }
    [ForeignKey("ReportsTo")]
    public virtual IList<User> ReportsChild { get; set; }
}

public class City
{
    [Key]
    [DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
    public int CityID { get; set; }
    //------------------------------------------------------------//
    [Required, MaxLength(20)]
    [LocalizedAttribute("Name")]
    public string Name { get; set; }
    //------------------------------------------------------------//
    [LocalizedAttribute("PhoneCode")]
    public int PhoneCode { get; set; }
    //------------------------------------------------------------//
    [Required, MaxLength(10)]
    public int ModifiedDate { get; set; }
}

public class CityUser
{
    [Key]
    [DatabaseGenerated(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Identity)]
    public int CityUserID { get; set; }
    //------------------------------------------------------------//
    [Required]
    public long ModifiedByUserID { get; set; }
    [ForeignKey("ModifiedByUserID")]
    public virtual User OperatorUser { get; set; }
    //------------------------------------------------------------//
    [Required]
    public int CityID { get; set; }
    [ForeignKey("CityID")]
    public virtual City City { get; set; }
}

But as EF5 goes for creating the database the error mentioned earlier comes out!!! What can I do for that?? I've read so many weblogs for that done some amendment on the Data Model.. But still cannot get ride of that error.... By the way, I want to declare relationships using DataAnnotations.

Now is there anyone who can get me out of this problem???!!!! :(

Regards,

Answer 1

Finally, I could come over this after hours and lots of efforts and by this way will never and ever forget the concept!!! :D The solution found:

modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();