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HomeDatabaseMysql TutorialEF Code First Migrations数据库迁移

1、EF Code First创建数据库 新建控制台应用程序Portal,通过程序包管理器控制台添加EntityFramework。 在程序包管理器控制台中执行以下语句,安装EntityFramework。 PM Install-Package EntityFramework 安装成功后,界面提示如下图: 在新建的Portal控制台

1、EF Code First创建数据库

  新建控制台应用程序Portal,通过程序包管理器控制台添加EntityFramework。

  在程序包管理器控制台中执行以下语句,安装EntityFramework。

PM> Install-Package EntityFramework

  安装成功后,界面提示如下图:

EF Code First Migrations数据库迁移

   在新建的Portal控制台应用程序中添加两个实体类,代码结构如下:

EF Code First Migrations数据库迁移

  其中,类文件PortalContext.cs的代码如下:

<span>using</span><span> System;
</span><span>using</span><span> System.Collections.Generic;
</span><span>using</span><span> System.Linq;
</span><span>using</span><span> System.Text;

</span><span>using</span><span> System.Data.Entity;
</span><span>using</span><span> System.Data.Entity.Infrastructure;

</span><span>using</span><span> Portal.Entities;
</span><span>using</span><span> Portal.Mapping;

</span><span>namespace</span><span> Portal
{
    </span><span>public</span> <span>class</span><span> PortalContext : DbContext
    {
        </span><span>static</span><span> PortalContext()
        {
            Database.SetInitializer(</span><span>new</span> DropCreateDatabaseIfModelChanges<portalcontext><span>());
        }

        </span><span>public</span> DbSet<province> Provinces { <span>get</span>; <span>set</span><span>; }
        </span><span>public</span> DbSet<category> Categories { <span>get</span>; <span>set</span><span>; }

        </span><span>protected</span> <span>override</span> <span>void</span><span> OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(</span><span>new</span><span> ProvinceMap());
            modelBuilder.Configurations.Add(</span><span>new</span><span> CategoryMap());
        }
    }
}</span></category></province></portalcontext>

  在静态构造函数中,设置了当数据库模型发生改变时,则删除当前数据库,重建新的数据库。

  代码执行后,生成的数据库:

 EF Code First Migrations数据库迁移

2、EF Code First数据库迁移

2.1、生成数据库

  修改类文件PortalContext.cs的静态构造函数,取消当数据库模型发生改变时删除当前数据库重建新数据库的设置。

<span>static</span><span> PortalContext()
{
    Database.SetInitializer</span><portalcontext>(<span>null</span><span>);
}</span></portalcontext>

   1>、在程序包管理器控制台,执行语句:

PM> Enable-Migrations -EnableAutomaticMigrations

 EF Code First Migrations数据库迁移

  执行成功后,Portal控制台应用程序代码结构中,添加Migrations文件夹,并生成类文件Configuration.cs。

EF Code First Migrations数据库迁移

<span>namespace</span><span> Portal.Migrations
{
    </span><span>using</span><span> System;
    </span><span>using</span><span> System.Data.Entity;
    </span><span>using</span><span> System.Data.Entity.Migrations;
    </span><span>using</span><span> System.Linq;

    </span><span>internal</span> <span>sealed</span> <span>class</span> Configuration : DbMigrationsConfiguration<portal.portalcontext><span>
    {
        </span><span>public</span><span> Configuration()
        {
            AutomaticMigrationsEnabled </span>= <span>true</span><span>;
        }

        </span><span>protected</span> <span>override</span> <span>void</span><span> Seed(Portal.PortalContext context)
        {
            </span><span>//</span><span>  This method will be called after migrating to the latest version.

            </span><span>//</span><span>  You can use the DbSet<t>.AddOrUpdate() helper extension method 
            </t></span><span>//</span><span>  to avoid creating duplicate seed data. E.g.
            </span><span>//</span>
            <span>//</span><span>    context.People.AddOrUpdate(
            </span><span>//</span><span>      p => p.FullName,
            </span><span>//</span><span>      new Person { FullName = "Andrew Peters" },
            </span><span>//</span><span>      new Person { FullName = "Brice Lambson" },
            </span><span>//</span><span>      new Person { FullName = "Rowan Miller" }
            </span><span>//</span><span>    );
            </span><span>//
</span><span>        }
    }
}</span></portal.portalcontext>

   2>、在程序包管理器控制台,执行语句:

PM> Add-Migration InitialCreate

EF Code First Migrations数据库迁移

  执行成功后,在Migrations文件夹中新增类文件201309201556388_InitialCreate.cs

EF Code First Migrations数据库迁移

  3>、在程序包管理器控制台,执行语句:

PM> Update-Database -Verbose

  执行结果生成与上面一致的数据库

EF Code First Migrations数据库迁移

  4>、在数据库模型中添加City类,执行程序包管理器控制台语句,Migrations文件夹中新增类文件201309201643300_AddCity.cs。

PM> Add-Migration AddCity

  再次执行程序包管理器控制台语句

PM> Update-Database -Verbose

EF Code First Migrations数据库迁移

  Portal控制台应用程序的代码结构:

EF Code First Migrations数据库迁移

  数据库更新成功之后,在数据库中新增表City。

EF Code First Migrations数据库迁移

2.2、版本回溯

  修改数据库中表City,删除其中字段ProvinceNo。在程序包管理器控制台中执行以下两条语句:

PM> Add-Migration ModifyCity

PM> Update-Database -Verbose

  执行成功之后,City表结构修改为:

EF Code First Migrations数据库迁移

  执行程序包管理器控制台语句,进行数据库版本回溯。

PM> Update-Database –TargetMigration:<span>"</span><span>201309201643300_AddCity.cs</span><span>"</span>

2.3、生成数据库版本之间的Sql脚本

  执行程序包管理器控制台语句,生成数据库版本之间的Sql脚本。该操作仅为生成Sql语句,并未在数据库中进行执行。

Update-Database -Script -SourceMigration:<span>"</span><span>201309201643300_AddCity.cs</span><span>"</span> -TargetMigration:<span>"</span><span>201309201708043_ModifyCity.cs</span><span>"</span> 

  其中-TargetMigration在未指定的情况,默认为迁移到最新的版本。

3、EF Code First Migrations语句的其他参数

1>、为指定的DbContext启用数据库迁移

PM> Enable-Migrations -ContextTypeName Portal.PortalContext

2>、设置是否允许自动迁移

Enable-Migrations

生成的Configuration.cs类文件的构造函数

<span>public</span><span> Configuration()
{
      AutomaticMigrationsEnabled </span>= <span>false</span><span>;
}</span>

3>、Enable-Migrations指定项目名称

PM> Enable-Migrations -StartUpProjectName Portal

如果在“Package Manager Console”中选择了默认项目可以不设置“-StartUpProjectName”参数;如果多次执行此命令可以添加-Force参数。

4>、查看所执行的Sql语句 -Verbose指令

Update-Database -Verbose 

4、代码下载

Portal.zip

5、参考资料

http://msdn.microsoft.com/en-US/data/jj591621

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