C＃MVC 5：如何将新表添加到现有数据库

Question

I want to add a new table in my database which my MVC 5 Project generated (with tables like: adoNetRoles , adoNetUser etc..).. I want my table to have two foreign keys on a user.. here is what my POCO-class looks like:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;
using System.ComponentModel.DataAnnotations.Schema;

namespace GameApp.Models
{
    [Table("Invitation")]
    public class Invitation 
    {
         public string Host { get; set; }
         public string Invitee { get; set; }
    }

    public class InvitationContext : DbContext
    {
        public InvitationContext()
        {
            if (Database.Exists())
            {
                Database.Initialize(true);
            }
        }
        public DbSet<Invitation> Inv { get; set; }
    }
}

I really don't know where to put this code and how to set the foreign key. I enabled CodeFirst-Migrations already and know how it works. I know how all this works if I would create my own project and database.. but the mvc5 project confuses me. Please help me because Google couldn't!

Answer 1

I think the "existing database" bit is throwing people. What you're calling an "existing database" seems to be simply the tables generated by Identity, as part of your application. In other words, the whole thing is Code First, but you've already done the initial migration.

The default MVC 5 project with individual auth gives you, among other things, a context, ApplicationDbContext , and a user entity, ApplicationUser , out of the box. You will simply, then, just extend these. Namely, you will add a new DbSet to ApplicationDbContext , rather than creating a new context ( InvitationContext ). Generally speaking, one context == one database. If you want Invitation and ApplicationUser to interact, then they both need to be in the same context. Then, you will add a foreign key(s) to Invitation . If I understand the relationship: user has many invitations (as host) and invitation has one host, and user has many invitations (as invitee) and invitation has one invitee. In other words, you've got two foreign keys to a "user" per invitation, resulting in two separate one-to-many relationships to the same table.

public class Invitation
{
    [Key]
    public int Key { get; set; }

    [ForeignKey("Host")]
    public string HostId { get; set; }
    public virtual ApplicationUser Host { get; set; }

    [ForeignKey("Invitee")]
    public string InviteeId { get; set; }
    public virtual ApplicationUser Invitee { get; set; }
}

Answer 2

Assuming you already know how Code-first migrations works here what is missing for your code:

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Data.Entity; 
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace GameApp.Models 
{ 
   [Table("Invitation")] 
   public class Invitation 
   { 
      [Key]
      public int Key { get; set; }
      public string Host { get; set; } 
      public string Invitee { get; set; } 
   }

   public class InvitationContext : DbContext
   {
      public InvitationContext() : base("YourConnectionString")
      { }

      public DbSet<Invitation> Inv { get; set; }
   }
}

I highly recomend you to separate tables and context in diferent files for better maintainability. Understanding what I did now:

//I don't think you need this line and if you need it the condition should have a !
if (Database.Exists())
{
    Database.Initialize(true);
}

//The constructor of DbContext can be empty, but it facilitates your work if you pass the connection string
public InvitationContext() : base("YourConnectionString")

//Use the anotation Key say to code-first migrations what is your, well, your key. Se set one key and then migrate your database.
[Key]
public int Key { get; set; }

It mostly problems with code-first than MVC, just some adjusts and you're ready to go.

source: http://www.dotnet-tricks.com/Tutorial/entityframework/R54K181213-Understanding-Entity-Framework-Code-First-Migrations.html