EF 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：
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：
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：
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
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。
<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
执行成功后，在Migrations文件夹中新增类文件201309201556388_InitialCreate.cs
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
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
Portal控制台应用程序的代码结构：
数据库更新成功之后，在数据库中新增表City。
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：
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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