最近学习了Entity Framework,对code first很感兴趣，赶紧学习下，部署很烦所以在这边写点备注
code first 有个migration的概念（迁移？）数据创建更新都是围绕这个词
1、使用初始化的数据库
1）创建个DEMO控制台项目
2）使用NuGet下载最新版本的EF，我下了EF5，DLL版本信息是4.4
打开
- Tools –> Library Package Manager –> Package Manager Console
输入Install-Package EntityFramework
现在写类文件
using System.Data.Entity;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Data.Entity.Infrastructure;
namespace MigrationsDemo
{
public class BlogContext : DbContext
{
public DbSet<Blog> Blogs { get; set; }
}
public class Blog
{
public int BlogId { get; set; }
public string Name { get; set; }
}
在DEMO的MAIN函数写对类的操作
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace MigrationsDemo
{
class Program
{
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();
}
}
}
记的APP.CONFIG要配置连接字符串
如下
<connectionStrings>
<add name="test" providerName="System.Data.SqlClient" connectionString="Password=123;Persist Security Info=True;User ID=sa;Initial Catalog=test;Data Source=;" />
</connectionStrings>
2、配置migration
增加个属性
public string Url { get; set; }
如果直接使用由于在数据库没有映射会报错
1、
3、运行magration
namespace MigrationsDemo.Migrations
{
using System;
using System.Data.Entity.Migrations;
public partial class AddBlogUrl : DbMigration
{
public override void Up()
{
AddColumn("Blogs", "Url", c => c.String());
}
public override void Down()
{
DropColumn("Blogs", "Url");
}
}
}
DOWN函数式回滚时候使用的
4、定制化
- public int Rating { get; set; }
再加个类
public class Post
{
public int PostId { get; set; }
[MaxLength(200)]
public string Title { get; set; }
public string Content { get; set; }
public int BlogId { get; set; }
public Blog Blog { get; set; }
}
增加字段的一些定制
namespace MigrationsCodeDemo.Migrations
{
using System;
using System.Data.Entity.Migrations;
public partial class AddPostClass : DbMigration
{
public override void Up()
{
CreateTable(
"Posts",
c => new
{
PostId = c.Int(nullable: false, identity: true),
Title = c.String(maxLength: 200),
Content = c.String(),
BlogId = c.Int(nullable: false),
})
.PrimaryKey(t => t.PostId)
.ForeignKey("Blogs", t => t.BlogId, cascadeDelete: true)
.Index(t => t.BlogId)
.Index(p => p.Title, unique: true);
AddColumn("Blogs", "Rating", c => c.Int(nullable: false, defaultValue: 3));
}
public override void Down()
{
DropIndex("Posts", new[] { "Title" });
DropIndex("Posts", new[] { "BlogId" });
DropForeignKey("Posts", "BlogId", "Blogs");
DropColumn("Blogs", "Rating");
DropTable("Posts");
}
}
}
运行 Add-Migration AddPostClass in Package Manager Console. 生成MIGRATION文件
然后运行 Update-Database –Verbose ：
–Verbose参数作用是打出运行的SQL 5、自定义更新
public string Abstract { get; set; }
1、Run the Add-Migration AddPostAbstract command in Package Manager Console.
如果这个字段需要初始化为POST字段的左边100字符，我们可以再
AddPostAbstract 文件的UP函数增加namespace MigrationsCodeDemo.Migrations { using System; using System.Data.Entity.Migrations; public partial class AddPostAbstract : DbMigration { public override void Up() { AddColumn("Posts", "Abstract", c => c.String()); Sql("UPDATE Posts SET Abstract = LEFT(Content, 100) WHERE Abstract IS NULL"); } public override void Down() { DropColumn("Posts", "Abstract"); } }}
Run the Update-Database –Verbose command in Package Manager Console.
就可以看出执行的初始化
6、执行到某个版本（包含回滚哟）
Update-Database –TargetMigration: AddBlogUrlAddBlogUrl ：为要回滚的目标文件名称清空数据库命令：Update-Database –TargetMigration: $InitialDatabase
7、SQL脚本
-Script ：加上这个参数VS会显示执行的SQL语句 ，从语句可以看到CODE FIRST 使用系统表dbo.__MigrationHistory进行版本控制
8、在程序启动时候自动执行，（初始化到最新版本）
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Entity;
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();
}
}
}
Database.SetInitializer(new MigrateDatabaseToLatestVersion<BlogContext, Configuration>()); ：将会将数据库初始化最新版本!
记得加入程序生成的MIGRATIONS的响应命名空间
初始化不会删除旧数据
好这次就到这里