在MVC3相同类型的实体之间的许多一对多的关系

问题描述

我有一个ASP.NET MVC3应用程序，其中我使用实体框架4.3 code-第一和迁移。

I have an ASP.NET MVC3 application, where I use Entity Framework 4.3 Code-First and Migrations.

我一直在试图创建同一类型的实体之间的许多一对多的关系，但是当我用脚手架迁移的迁移，它会产生一个一对一的关系。

I've been trying to create a many-to-many relationship between entities of the same type, but when I scaffold the migration with Migrations, it generates a one-to-one relationship.

的想法是，一​​个用户应能跟随多个其他用户（认为微）

The idea is that one user should be able to follow multiple other users (think Twitter).

我的用户模型是这个样子：

public class User
{
    public int UserId { get; set; }
    public string Name { get; set; }
    public DateTime Registered { get; set; }
    ...
    public virtual ICollection<User> Follows { get; set; }
}

在我的脚手架增加跟随属性，我得到这样一个迁移：

When I scaffold the the added Follows-property, I get a migration like this:

public partial class FollowUser : DbMigration
{
    public override void Up()
    {
        AddColumn("User", "User_UserId", c => c.Int());
        AddForeignKey("User", "User_UserId", "User", "UserId");
        CreateIndex("User", "User_UserId");
    }

    ...
}

所以，实体框架间$ P $其中pts我的模型，两个用户之间的一对一的关系。

So Entity Framework interprets my model as a one-to-one relationship between two users.

如何创建一个多到许多相同类型的实体之间的关系？

推荐答案

由于它是一个多对多的自我加盟关系，用户实体应该有一个关注和继类型用户两个属性。因此，让我们改变你的类包括那些

Since It is a Many to Many Self Joined relationship, User entity should have a Followers and Following properties both of Type User. So Let us alter your class to include those

public class User
{
    public int ID { get; set; }
    public string Name { get; set; }       
    public virtual ICollection<User> Followers { get; set; }
    public virtual ICollection<User> Following { get; set; }
}

现在更新的DbContext类有它返回一个用户属性

Now update the DbContext class to have a Property which returns the Users

 public DbSet<User> Users { set; get; }

我们需要告诉的EntityFramework，我们需要有一个许多人在这两者之间的关系很多船。因此，让我们做，与流利的API通过覆盖 OnModelCreating 法

We need to tell EntityFramework that we need to have a many to many relations ship between these two. So Let us do that with Fluent API by overriding OnModelCreating method

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<User>().HasMany(m => m.Followers).WithMany(p => p.Following).Map(w => w.ToTable("User_Follow").MapLeftKey("UserId").MapRightKey("FollowerID"));
    base.OnModelCreating(modelBuilder);
}

现在实体框架将创建表是这样的。

Now Entity Framework will create the tables like this.

请注意，我们明确告诉实体框架使用用户ID 和 FollowerId 作为Forign键列名。如果我们还没有提到的是，EF将使用 USER_ID 和 User_ID1 作为列名。

Note that we explicitly told Entity Framework to use UserId and FollowerId as the Forign Key column name. If we havent mentioned that, EF will use User_ID and User_ID1 as the column names.

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