如何启用迁移以更新 MVC4 中的数据库?

How to Enable Migration to update my database in MVC4?(如何启用迁移以更新 MVC4 中的数据库?)

问题描述

我正在开发一个在 Visual Studio 2012 中使用 MVC4 的项目，并在表格中添加了一列.

I'm working on a project using MVC4 in Visual Studio 2012 and have added a column in the table.

现在当我想调试我的项目时，错误提示要使用迁移来更新我的数据库.

Now when I want to debug my project the error says to use the migration to update my database.

我必须做什么?

我搜索了很多，发现了一些方法，例如:

I have been searching a lot and found some methods like:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
  Database.SetInitializer<ResTabelaIndex>(null);
}

Enable-Migrations -EnableAutomaticMigrations

My Model Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration.Conventions;
using System.Data.Entity.Migrations;
using System.ComponentModel.DataAnnotations;
using System.Data.Entity.Infrastructure;

namespace Vista.Models
{
    public class TabelaIndex
    {
        public int ID { get; set; }
        public string n_empresa { get; set; }
        public string titulo{ get; set; }
        public string url { get; set; }
        public string imagens { get; set; }
    }

    public class DefaultConnection : DbContext
    {
        public DbSet<TabelaIndex> ResTabelaIndex { get; set; }
    }

}

错误是说你有两个上下文.当您第一次使用 MVC 4 创建项目时，Visual Studio 默认为您的 SimpleMembership 创建一个上下文(检查 Models/Account.cs)或为 ctrl+f 执行code>UsersContext，如果你不使用SimpleMembership，你可以删除这个文件.删除此上下文后，继续将以下内容添加到您的 DefaultConnection 类中:

The error is saying that you have two contexts. When you first create a project using MVC 4, Visual Studio creates a context for your SimpleMembership by default (check Models/Account.cs) or do a ctrl+f for UsersContext, you can just delete this file if you are not using SimpleMembership. After removing this context, go ahead and add the following to your DefaultConnection class:

protected override void OnModelCreating(DbModelBuilder builder)
{
   Database.SetInitializer(new MigrateDatabaseToLatestVersion<DefaultConnection,Configuration>());
}

如果您正确启用了迁移，您还应该有一个名为 Migrations 的文件夹，其中有一个 Configuration 类，它的构造函数应该如下所示(如果您想启用自动迁移):

If you enabled migrations correctly you should also have a folder called Migrations and inside it a Configuration class, its constructor should look like this (if you want to enable automatic migrations):

public Configuration()
{
   AutomaticMigrationsEnabled = true;
}

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