How to add 2 foreign keys and their corresponding navigation properties to a model

Question

User-186068080 posted

Hi all

I a newcomer in asp.net mvc and i got stuck with a trivial problem for hours. I have a simple class that models a message. its here:

public class Message
{
    [Key]
    public int Id { get; set; }

    // AspNetUsers
    public ApplicationUser Sender { get; set; }
    public ApplicationUser Receiver { get; set; }

    // SenderId of the message
    [Required]
    [ForeignKey("Sender")]
    [Display(Name = "Sender")]
    [InverseProperty("MessageSenderId")]
    public string SenderId { get; set; }

    // ReceiverId of this message
    [Required]
    [ForeignKey("Receiver")]
    [Display(Name = "Receiver")]
    [InverseProperty("MessageReceiverId")]
    public string ReceiverId { get; set; }

    // other properties
}

The SenderId and ReceiverId are the Id of sender and receiver of this message respectively. The Sender and Receiver are navigation properties to fetch them from database when i want to pass the message model to view.

Unfortunately, when i want to add a new migration, this error is raised: The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Mails_dbo.AspNetUsers_ReceiverId". The conflict occurred in database "DbName", table "dbo.AspNetUsers", column 'Id'.

The message class before changing was:

public class Message
{
    public int Id { get; set; }

    // No Navigation is defined

    // SenderId of the message
    [Required]
    [Display(Name = "Sender")]
    public string SenderId { get; set; }

    // ReceiverId of this message
    [Required]
    [Display(Name = "Receiver")]
    public string ReceiverId { get; set; }

    // other properties
}

What can i do? Thanks

Answer 1

User-832373396 posted

Hi Ehsan,

How to add 2 foreign keys and their corresponding navigation properties to a model

Please change a bit to your current code, then it will work.

Here is the testing working example;

• 1 find the class ApplicationUser   and add navigation properties ;

   public class ApplicationUser : IdentityUser
    {
        public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager, string authenticationType)
        {
            // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
            var userIdentity = await manager.CreateIdentityAsync(this, authenticationType);
            // Add custom user claims here
            return userIdentity;
        }
        [InverseProperty("Sender")]
        public virtual ICollection<Message> SenderMessages { get; set; }
        [InverseProperty("Receiver")]
        public virtual ICollection<Message> ReceiverMessages { get; set; }
    }

• 2 remove InverseProperty  attribute to SenderId and ReceiverId 

public class Message
    {
        [Key]
        public int Id { get; set; }

        // AspNetUsers
        public virtual ApplicationUser Sender { get; set; }
        public virtual ApplicationUser Receiver { get; set; }

        // SenderId of the message
        [Required]
        [ForeignKey("Sender")]
        [Display(Name = "Sender")]
      //  [InverseProperty("MessageSenderId")]
        public string SenderId { get; set; }

        // ReceiverId of this message
        [Required]
        [ForeignKey("Receiver")]
        [Display(Name = "Receiver")]
     //   [InverseProperty("MessageReceiverId")]
        public string ReceiverId { get; set; }

        // other properties
    }

• 3 open Package Manager Console and type the command

PM> Add-Migration ee1

• 4 find the 201802050240405_ee1.cs file from Migrations folder and change  .ForeignKey("dbo.AspNetUsers", t => t.ReceiverId, cascadeDelete: true)  to  .ForeignKey("dbo.AspNetUsers", t => t.ReceiverId, cascadeDelete: false)

  public partial class ee1 : DbMigration
    {
        public override void Up()
        {
         
            CreateTable(
                "dbo.Messages",
                c => new
                    {
                        Id = c.Int(nullable: false, identity: true),
                        SenderId = c.String(nullable: false, maxLength: 128),
                        ReceiverId = c.String(nullable: false, maxLength: 128),
                    })
                .PrimaryKey(t => t.Id)
                .ForeignKey("dbo.AspNetUsers", t => t.ReceiverId, cascadeDelete: false)
                .ForeignKey("dbo.AspNetUsers", t => t.SenderId, cascadeDelete: false)
                .Index(t => t.SenderId)
                .Index(t => t.ReceiverId);
            
        }
      ...
    }

• 5. Ok. Everything is right and we can view the picture;

Guide

http://www.entityframeworktutorial.net/code-first/inverseproperty-dataannotations-attribute-in-code-first.aspx 

With regards, Angelina Jolie

Answer 2

User-186068080 posted

Thanks AngelinaJoli for your complete answer.

But i come to another question. Since i never want to navigate back from user to his mail, does it impose extra load to server?