如何获得“实体框架代码优先”迁移来查看我的模型？

Question

I made a new ASP.Net Web Application and enabled migrations on it. I ran add-migration initial and the initial migration does in fact have all the default tables for authentication (dbo.AspNetRoles, dbo.AspNetUserRoles, etc). However, when I create my own context and add an entity model to it, I can't get migrations to acknowledge that model. That is, when I run add-migration added-watchedgame-model I just get an "empty" migration file. So what am I doing wrong? Does my DbContext have to be referenced somehow? can Entity Framework only handle migrations for 1 dbcontext?

ReleaseDateMailerDBContext.cs:

using System.Data.Entity;
using WebApplication4.Models;

namespace WebApplication4.DataAccess
{
    public class ReleaseDateMailerDBContext : DbContext
    {
        public ReleaseDateMailerDBContext() : base("DefaultConnection") { }

        public DbSet<WatchedGameModel> WatchedGameModelSet { get; set; }
    }
}

WatchedGameModel.cs:

using System.ComponentModel.DataAnnotations;

namespace WebApplication4.Models
{
    public class WatchedGameModel
    {
        public int ID { get; set; }
        [MaxLength(1024)]
        public string URL { get; set; }
        public string Email { get; set; }
        public bool EmailSent { get; set; }
    }
}

"empty" migration file:

namespace ReleaseDateMailer.Migrations
{
    using System;
    using System.Data.Entity.Migrations;

    public partial class addedwatchedgamemodel : DbMigration
    {
        public override void Up()
        {
        }

        public override void Down()
        {
        }
    }
}

Answer 1

"Batch Clean" may resolve your porblem.

It suggests that the EF tooling/assemblies are looking in a location other than the default build output location (typically /bin/Debug). The clean command also, incidentally, clears intermediary outputs.

To do a batch clean:

1. Select Build -> Batch Build
2. Click Select All
3. Click Clean

Close dialog, rebuild and re-attempt migration.

Answer 2

While running the add-migration command your package manager console should be pointed to the project having your DBContext class (WebApplication4.DataAccess). If you have migration in a different project than your web application project (suppose WebApplication4.Web) then you should run the following command:

add-migration "MigrationName" -projectName:WebApplication.DataAccess -startupProjectName:WebApplication4.Web

Hope it helps!!

Answer 3

• With the built-in asp.net mvc project, a DbContext class ( ApplicationDbContext ) is already created!
• When you enter enable-migrations , a migration configuration class is created based on the dbcontext class that it finds.
• When you enter add-migration "migrationname" , That dbcontext class is what is checked for differences.

So all one has to do is, rather than making one's own class that derives from DbContext , use that one.