Entity Framework Code First （八）迁移 Migrations

创建初始模型和数据库

　　在开始使用迁移（Migrations）之前，我们需要一个 Project 和一个 Code First Model, 对于本文将使用典型的 Blog 和 Post 模型

创建一个新的控制台应用程序 MigrationsDemo;

添加最新的 EntityFramework 到项目

Tools –> Library Package Manager –> Package Manager Console;

运行命令 Install-Package EntityFramework　　

创建 Blog.cs 和 DbContext 的派生类 BlogContext.cs

public class Blog
{
public int BlogId { get; set; }
public string Name { get; set; }
}

public class BlogContext : DbContext
{
public DbSet<Blog> Blogs { get; set; }
}

　　更改 Program.cs 以调用

static void Main(string[] args)
{
using (var db = new BlogContext())
{
db.Blogs.Add(new Blog { Name = "Another Blog" });
db.SaveChanges();

foreach (var blog in db.Blogs)
{
Console.WriteLine(blog.Name);
}
}

Console.WriteLine("Press any key to exit...");
Console.ReadKey();
}

　　运行查看结果

DECLARE @CurrentMigration [nvarchar](max)

IF object_id('[dbo].[__MigrationHistory]') IS NOT NULL
SELECT @CurrentMigration =
(SELECT TOP (1)
[Project1].[MigrationId] AS [MigrationId]
FROM ( SELECT
[Extent1].[MigrationId] AS [MigrationId]
FROM [dbo].[__MigrationHistory] AS [Extent1]
WHERE [Extent1].[ContextKey] = N'MigrationsDemo.BlogContext'
)  AS [Project1]
ORDER BY [Project1].[MigrationId] DESC)

IF @CurrentMigration IS NULL
SET @CurrentMigration = '0'

IF @CurrentMigration < '201312240822431_InitialCreate'
BEGIN
CREATE TABLE [dbo].[Blogs] (
[BlogId] [int] NOT NULL IDENTITY,
[Name] [nvarchar](max),
CONSTRAINT [PK_dbo.Blogs] PRIMARY KEY ([BlogId])
)
CREATE TABLE [dbo].[__MigrationHistory] (
[MigrationId] [nvarchar](150) NOT NULL,
[ContextKey] [nvarchar](300) NOT NULL,
[Model] [varbinary](max) NOT NULL,
[ProductVersion] [nvarchar](32) NOT NULL,
CONSTRAINT [PK_dbo.__MigrationHistory] PRIMARY KEY ([MigrationId], [ContextKey])
)
INSERT [dbo].[__MigrationHistory]([MigrationId], [ContextKey], [Model], [ProductVersion])
VALUES (N'201312240822431_InitialCreate', N'MigrationsDemo.BlogContext',  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
END

IF @CurrentMigration < '201312310618077_AddBlogUrl'
BEGIN
ALTER TABLE [dbo].[Blogs] ADD 

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MigrationsDemo.Migrations;

namespace MigrationsDemo
{
class Program
{
static void Main(string[] args)
{
Database.SetInitializer(new MigrateDatabaseToLatestVersion<BlogContext, Configuration>());

using (var db = new BlogContext())
{
db.Blogs.Add(new Blog { Name = "Another Blog " });
db.SaveChanges();

foreach (var blog in db.Blogs)
{
Console.WriteLine(blog.Name);
}
}

Console.WriteLine("Press any key to exit...");
Console.ReadKey();
}
}
}


原文：[url=http://msdn.microsoft.com/en-us/data/jj591621]http://msdn.microsoft.com/en-us/data/jj591621" target=_blank> [nvarchar](max)
INSERT [dbo].[__MigrationHistory]([MigrationId], [ContextKey], [Model], [ProductVersion])
VALUES (N'201312310618077_AddBlogUrl', N'MigrationsDemo.BlogContext',  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
END

IF @CurrentMigration < '201312310648099_AddPostClass'
BEGIN
CREATE TABLE [dbo].[Posts] (
[PostId] [int] NOT NULL IDENTITY,
[Title] [nvarchar](200),
[Content] [nvarchar](max),
[BlogId] [int] NOT NULL,
CONSTRAINT [PK_dbo.Posts] PRIMARY KEY ([PostId])
)
CREATE INDEX [IX_BlogId] ON [dbo].[Posts]([BlogId])
CREATE UNIQUE INDEX [IX_Title] ON [dbo].[Posts]([Title])
ALTER TABLE [dbo].[Blogs] ADD [Rating] [int] NOT NULL DEFAULT 3
ALTER TABLE [dbo].[Posts] ADD CONSTRAINT [FK_dbo.Posts_dbo.Blogs_BlogId] FOREIGN KEY ([BlogId]) REFERENCES [dbo].[Blogs] ([BlogId]) ON DELETE CASCADE
INSERT [dbo].[__MigrationHistory]([MigrationId], [ContextKey], [Model], [ProductVersion])
VALUES (N'201312310648099_AddPostClass', N'MigrationsDemo.BlogContext',  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
END

IF @CurrentMigration < '201312310729575_AddPostAbstract'
BEGIN
ALTER TABLE [dbo].[Posts] ADD [Abstract] [nvarchar](max)
UPDATE dbo.Posts SET Abstract = LEFT(Content, 100) WHERE Abstract IS NULL
INSERT [dbo].[__MigrationHistory]([MigrationId], [ContextKey], [Model], [ProductVersion])
VALUES (N'201312310729575_AddPostAbstract', N'MigrationsDemo.BlogContext',  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
END[/code]

View Code

产生幂等脚本（EF6+）

　　从 EF6 开始，如果你使用 –SourceMigration $InitialDatabase， 产生的脚本将是幂等的，幂等脚本意味着无论数据库当前处于什么版本/状态，都能升级至最新版本或指定版本（指定 –TargetMigration），生成的脚本包括检查表 __MigrationsHistory 的逻辑以及只更新之前从未更新的

在应用程序启动时自动升级（MigrateDatabaseToLatestVersion初始化器）

　　当你发布部署应用程序的时候，可能希望当程序启动的时候它自动更新数据库（更新应用任何未更新的迁移），你可以通过注册 MigrateDatabaseToLatestVersion 数据库初始化器来实现这一点，数据库初始化器只包含一些逻辑检查用于确保数据库被正确设置，这个逻辑检查将会在AppDomain 的 context 第一次被使用的时候执行。

　　当我们创建一个初始化器的实例时，需要指定 context type（BlogContext）以及 migrations configuration （Configuration）- 这个迁移配置类是在我们启用迁移时生成的 Migrations 目录下增加的



using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MigrationsDemo.Migrations;

namespace MigrationsDemo
{
class Program
{
static void Main(string[] args)
{
Database.SetInitializer(new MigrateDatabaseToLatestVersion<BlogContext, Configuration>());

using (var db = new BlogContext())
{
db.Blogs.Add(new Blog { Name = "Another Blog " });
db.SaveChanges();

foreach (var blog in db.Blogs)
{
Console.WriteLine(blog.Name);
}
}

Console.WriteLine("Press any key to exit...");
Console.ReadKey();
}
}
}


原文：[url=http://msdn.microsoft.com/en-us/data/jj591621]http://msdn.microsoft.com/en-us/data/jj591621