EF Code First Migrations数据库迁移

2017-01-10 08:19:05来源:cnblogs.com作者:迪克猪人点击

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1、EF Code First创建数据库

步骤1:新建控制台应用程序

步骤2:安装EntityFramework

在程序包管理器控制台中执行以下语句:

PM>Install-Package EntityFramework

2、项目结构

image

两个实体及映射,PortalContext代码如下:

using System;using System.Collections.Generic;using System.Data.Common;using System.Data.Entity;using System.Linq;using System.Text;using System.Threading.Tasks;using Portal.Enities;using Portal.Mapping;namespace Portal{    public class PortalContext : DbContext    {        static PortalContext()        {            System.Data.Entity.Database.SetInitializer<PortalContext>(null);           //Database.SetInitializer(new DropCreateDatabaseAlways<PortalContext>());        }        public DbSet<Category> Categories { get; set; }        public DbSet<Province> Provinces { get; set; }        /// <summary>        /// This method is called when the model for a derived context has been initialized, but        /// before the model has been locked down and used to initialize the context.  The default        /// implementation of this method does nothing, but it can be overridden in a derived class        /// such that the model can be further configured before it is locked down.        /// </summary>        /// <remarks>        /// Typically, this method is called only once when the first instance of a derived context        /// is created.  The model for that context is then cached and is for all further instances of        /// the context in the app domain.  This caching can be disabled by setting the ModelCaching        /// property on the given ModelBuidler, but note that this can seriously degrade performance.        /// More control over caching is provided through use of the DbModelBuilder and DbContextFactory        /// classes directly.        /// </remarks>        /// <param name="modelBuilder"> The builder that defines the model for the context being created. </param>        protected override void OnModelCreating(DbModelBuilder modelBuilder)        {            modelBuilder.Configurations.Add(new CategoryMap());            modelBuilder.Configurations.Add(new ProvinceMap());        }    }}

其他代码,可以从本博文最后下载。

3、EF Code First数据库迁移

步骤1:生成数据库

修改PortailContext.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数据库的设置。

static PortalContext()        {            System.Data.Entity.Database.SetInitializer<PortalContext>(null);            //Database.SetInitializer(new DropCreateDatabaseAlways<PortalContext>());        }

步骤2:在程序包管理器控制台,执行以下语句

PM>Enable-Migrations –EnableAutomaticMigrations

运行结果如下:

image

Configuration代码如下

namespace Portal.Migrations{    using System;    using System.Data.Entity;    using System.Data.Entity.Migrations;    using System.Linq;    internal sealed class Configuration : DbMigrationsConfiguration<Portal.PortalContext>    {        public Configuration()        {            AutomaticMigrationsEnabled = true;        }        protected override void Seed(Portal.PortalContext context)        {            //  This method will be called after migrating to the latest version.            //  You can use the DbSet<T>.AddOrUpdate() helper extension method             //  to avoid creating duplicate seed data. E.g.            //            //    context.People.AddOrUpdate(            //      p => p.FullName,            //      new Person { FullName = "Andrew Peters" },            //      new Person { FullName = "Brice Lambson" },            //      new Person { FullName = "Rowan Miller" }            //    );            //        }    }}

步骤3:在程序包管理器控制台执行以下语句

PM>Add-Migration InitialCreate

运行结果如下:

image

步骤4:在程序包管理器控制台执行以下语句

PM>Update-Database –Verbose

执行结果如下:

image

到此,数据完成了创建:

image

4、EF Code First添加实体

步骤1:增加City.cs实体

步骤2:在程序包管理器控制台执行以下语句:

PM>Add-Migration AddCity

执行结果如下:

image

步骤3:更新实体到数据库,在程序包管理器控制台执行以下语句

PM>Update-Database –Verbose

image

数据库变化如下:

image

5、EF Code First修改实体

步骤1:修改City,增加CityNo属性

步骤2:在程序包管理器控制台中执行以下代码:

PM>Add-Migration UpdateCity

执行结果如下:

image

步骤3:在程序包管理器控制台执行以下语句

PM>Update-Database –Verbose

执行结果如下:

image

image

6、版本回溯

步骤1:修改数据库中的City,删除CityNo字段

步骤2:在程序包管理器控制器执行以下语句:

PM>Add-Migration ModifyCity

image

步骤3:更新到数据库,在程序包管理器控制台执行以下语句:

PM>Update-Database –Verbose

image

在程序包管理器控制台执行以下语句:

PM>Update-Database –SourceMigration “201701091349455_AddCity.cs”

执行结果如下:

image

7、其他命令

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

public Configuration(){      AutomaticMigrationsEnabled = false;}

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 

8、示例下载

Portal示例下载:http://files.cnblogs.com/files/zsy/Portal.rar

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