ApplicationDbContext.cs

public class ApplicationDbContext : DbContext
{
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
        {
        }

        public DbSet<BookReadingEvent> BookReadingEvents { get; set; }
        public DbSet<Register> RegisterAccount { get; set; }
        public DbSet<Login> LoginAccount { get; set; }
}

Register model class:

namespace BookReadingEvents.Models
{
    [Index(nameof(Email), IsUnique = true)]
    public class Register
    {
        [Key]
        public int RegisterId { get; set; }

        [Required]
        [DataType(DataType.EmailAddress, ErrorMessage = "Please enter a valid e-mail address")]
        public string Email { get; set; }
        [Required]
        [Display(Name = "Full Name")]
        public string Name { get; set; }
        [Required]
        [DataType(DataType.Password)]
        [MinLength(5, ErrorMessage = "Password length cannot be less than 5")]
        public string Password { get; set; }

        [NotMapped] // Does not affect the database
        [Compare("Password")]
        [Required]
        [DataType(DataType.Password)]
        [Display(Name = "Confirm Password")]
        public string ConfirmPassword { get; set; }
    }
}

Login model class:

public class Login
{
        [Key]
        public int LoginId { get; set; }
        
        [Required]
        [DataType(DataType.EmailAddress, ErrorMessage = "Please enter a valid e-mail address")]
        public string Email { get; set; }
        
        [Required]
        [DataType(DataType.Password)]
        [MinLength(5, ErrorMessage = "Password length cannot be less than 5")]
        public string Password { get; set; }

        public DateTime EntryDate { get; set; } = DateTime.Now;

        [ForeignKey("Registers")]
        public int RegisterId { get; set; }
        public virtual Register Registers { get; set; }

        // Here foreign key is working fine
}

Book Reading Event model class:

public class BookReadingEvent
{
    [Key]
    public int Id { get; set; }
    [Required]
    public string Title { get; set; }

    [Required]
    [DataType(DataType.Date)]
    public DateTime Date { get; set; }

    [Required]
    public string Location { get; set; }
    public string StartTime { get; set; }
    public string EventType { get; set; }

    [Range(1,9999)]
    public int Duration { get; set; }

    [StringLength(50, ErrorMessage = "Description length can't be more than 50.")]
    public string Description { get; set; }

    [StringLength(500, ErrorMessage = "Other Details length can't be more than 500.")]
    public string Details { get; set; }

    public string InviteByEmail { get; set; }

    [ForeignKey("Registers")]
    public int RegisterId { get; set; }
    public virtual Register Registers { get; set; }
       
    // Error: The ALTER TABLE statement conflicted with the FOREIGN KEY constraint 
    // "FK_BookReadingEvents_RegisterAccount_RegisterId". The conflict occurred in database 
    // "BookReadingEvents", table "dbo.RegisterAccount", column 'RegisterId'.
}

I want to add foreign key RegisterId to the BookReadingEventModel as well, but I get an error while it is working fine with the Login model. How do I add foreign key to the Book Reading Event table with code-first approach?

CodePudding user response：

This error is caused if you have data in your database conflicting your change. It is easily tested by creating a completely new migration and running it on a new empty database.

You most likely have old test data in your database which can't have a reference.

CodePudding user response：

you have required RegisterId in several tables and this causes an error. Try to make RegisterId nullable in both classes

        public int? RegisterId { get; set; }

        [ForeignKey("RegisterId")]
        public virtual Register Register { get; set; }

and add navigaion properties to Register class too

public class Register
{
        [Key]
        public int RegisterId { get; set; }
         ....

      [InverseProperty(nameof(Login.Register))]
       public virtual ICollection<Register> LoginRegisters {get; set;}

       [InverseProperty(nameof(BookReadingEvent.Register))]
       public virtual ICollection<Register> BookReadingEventRegisters {get; set;}

}