为什么EF会生成外键？

Question

I need make one to one (optional).

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<PinnacleAccount>().HasKey(x => x.Id);

    modelBuilder.Entity<PinnacleAccount>()
        .HasRequired(x => x.User)
        .WithOptional(x => x.PinnacleAccount);

    base.OnModelCreating(modelBuilder);
}

and when I run 'Add-Migration Init' I check generated migration and see:

CreateTable(
                "dbo.PinnacleAccounts",
                c => new
                    {
                        Id = c.Int(nullable: false, identity: true),
                        ClientId = c.String(),
                        Password = c.String(),
                        PercentForBet = c.Int(nullable: false),
                        UserId = c.String(),
                        User_Id = c.String(nullable: false, maxLength: 128),
                    })
                .PrimaryKey(t => t.Id)
                .ForeignKey("dbo.AspNetUsers", t => t.User_Id)
                .Index(t => t.User_Id);

But I have property UserId. Why ef create User_Id

   public class ApplicationUser : IdentityUser
    {
        public virtual PinnacleAccount PinnacleAccount { get; set; }
        public int? PinnacleAccountId { get; set; }

        public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
        {
            // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
            var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
            // Add custom user claims here
            return userIdentity;
        }
    }

Answer 1

When you make a 1:0.1 relationship in entity framework, the primary key of the first entity must be same as the primary key of the second entity. You can't specify which property is the FK because it is not necessary. I will explain:

If a User has only one PinnacleAccount , it is a 1:0.1 relationship. So, every PinnacleAccount belongs to an User . It means that, PinnacleAccount is a weak entity, so, its primary key is also an User foreign key.

PinnacleAccount should not have its own Id, just the UserId. So, PinnacleAccount should be like this:

public class PinnacleAccount
{
    public string UserId { get; set; } //PK AND FK
    public string ClientId  { get; set; }
    public string Password { get; set; }
    public string PercentForBet { get; set; }
}

Mapping:

modelBuilder.Entity<PinnacleAccount>().HasKey(x => x.UserId);
modelBuilder.Entity<User>()
    .HasOptional(i => i.PinnacleAccount)
    .WithRequired(x => x.User);

This is the only way to make 1:0.1 relationship.

Hope it helps!

Answer 2

Maybe you need to declare in the model mapping the relationships

this.HasOptional(t => t.User)
                .WithMany(t => t.PinnacleAccount)
                .HasForeignKey(d => d.UserId);

Answer 3

As you know EF creates the model, and corresponding migrations, based on conventions, attributes, and the Fluent API you're using. And, unless you speciy otherwise, the convention areonly built-in conventions that works fine in most occassions.

As you're not explicilty specifying the FK property, conventions are being used. The "usual" convention would have chosen UserId as FK. However, there is a type mismatch, because PinnacleAccount 's UserId is simply a string, while, according to the created User_Id , the primary key on the AspNetUsers table, UserId is an string with lenght 128.

So, if you define the length of the UserId as 128, with [MaxLenght] attribute, or with .hasMaxLength() fluent API, conventions will use it for the foreing key.

Answer 4

@Fabio Luz has given the correct answer, but for anyone that already has an incorrect relationship set up and needs to correct it, here's how I did it.

My 'PinnacleAccount' looked like the following (I use GUIDs, but you get the idea):

public class PinnacleAccount
{
  [Required]
  [Key]
  [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
  public Guid Id { get; set; }

  public virtual ApplicationUser User { get; set;  }
  [Required]
  public virtual string UserId { get; set; }  
}

I could access the the User from PinnacleAccount, but not the other way around, which I wanted to correct. To do so, I had to create two migrations.

Firstly, I edited the UserId property to be UserIdOld and created the migration which looked like:

public override void Up()
{
    DropForeignKey("dbo.PinnacleAccount", "UserId", "dbo.AspNetUsers");
    DropIndex("dbo.PinnacleAccount", new[] { "UserId" });
    RenameColumn(table: "dbo.PinnacleAccount", name: "UserId", newName: "User_Id");
    AddColumn("dbo.PinnacleAccount", "UserIdOld", c => c.String(nullable: false));
    AlterColumn("dbo.PinnacleAccount", "User_Id", c => c.String(maxLength: 128));
    CreateIndex("dbo.PinnacleAccount", "User_Id");
    AddForeignKey("dbo.PinnacleAccount", "User_Id", "dbo.AspNetUsers", "Id");
}

public override void Down()
{
    DropForeignKey("dbo.PinnacleAccount", "User_Id", "dbo.AspNetUsers");
    DropIndex("dbo.PinnacleAccount", new[] { "User_Id" });
    AlterColumn("dbo.PinnacleAccount", "User_Id", c => c.String(nullable: false, maxLength: 128));
    DropColumn("dbo.PinnacleAccount", "UserIdOld");
    RenameColumn(table: "dbo.PinnacleAccount", name: "User_Id", newName: "UserId");
    CreateIndex("dbo.PinnacleAccount", "UserId");
    AddForeignKey("dbo.PinnacleAccount", "UserId", "dbo.AspNetUsers", "Id", cascadeDelete: true);
}

This allowed me to free up the UserId column name and it populated the User_Id column with the UserId (as that was the alter statement).

I then changed the the class to look like:

 public class PinnacleAccount
{
    public string UserId { get; set; }

  public virtual ApplicationUser User { get; set;  }
}

Followed by the changes to the Mapping as described by @Fabio Luz.

I then created a second migration which looked like:

public override void Up()
{
    DropIndex("dbo.PinnacleAccount", new[] { "User_Id" });
    RenameColumn(table: "dbo.PinnacleAccount", name: "User_Id", newName: "UserId");
    DropPrimaryKey("dbo.PinnacleAccount");
    AlterColumn("dbo.PinnacleAccount", "UserId", c => c.String(nullable: false, maxLength: 128));
    AddPrimaryKey("dbo.PinnacleAccount", "UserId");
    CreateIndex("dbo.PinnacleAccount", "UserId");
    DropColumn("dbo.PinnacleAccount", "Id");
    DropColumn("dbo.PinnacleAccount", "UserIdOld");
}

public override void Down()
{
    AddColumn("dbo.PinnacleAccount", "UserIdOld", c => c.String(nullable: false));
    AddColumn("dbo.PinnacleAccount", "Id", c => c.Guid(nullable: false, identity: true));
    DropIndex("dbo.PinnacleAccount", new[] { "UserId" });
    DropPrimaryKey("dbo.PinnacleAccount");
    AlterColumn("dbo.PinnacleAccount", "UserId", c => c.String(maxLength: 128));
    AddPrimaryKey("dbo.PinnacleAccount", "Id");
    RenameColumn(table: "dbo.PinnacleAccount", name: "UserId", newName: "User_Id");
    CreateIndex("dbo.PinnacleAccount", "User_Id");
}

That gave me the correct 1:0.1. Thanks to Fabio for showing how to create one properly!