mvc模型中MySQL类_Mvc5 EF6 CodeFirst Mysql (二) 修改数据模型

╰半橙微兮° 2022-11-08 11:25 176阅读 0赞

1.开发环境中修改模型，在DbContext中加入静态构造函数，并设置初始化模式：

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staticDemoDbContext()

Database.SetInitializer(new DropCreateDatabaseIfModelChanges());

如果是Mysql，需要在DbContext加上 \[DbConfigurationType(typeof(MySql.Data.Entity.MySqlEFConfiguration))\] 属性，否则操作数据库时会报错，更改结束后，注释掉就可以了

新增类时需要在DbContext添加该类的引用属性，如：新增Department类：

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public DbSet Departments \{ get; set; \}

2.生成环境中数据迁移

2.1 首先安装 Enitity Framework：Install-Package EntityFramework

2.2 修改DbContext静态构造函数：

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staticDemoDbContext()

Database.SetInitializer(null);

2.3 在程序包管理器控制台，执行语句：

PM> Enable-Migrations -EnableAutomaticMigrations

这时会在工程下建立文件夹：Migrations 和 Configuration.cs 文件

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internal sealed class Configuration : DbMigrationsConfiguration\{publicConfiguration()

AutomaticMigrationsEnabled= true;

\}protected override voidSeed(MvcDemo.DAL.DemoDbContext context)

\{//This method will be called after migrating to the latest version.//You can use the DbSet.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" \}//);//\}

2.4 执行语句：(为测试效果，删除了Student类中的Email和Score属性)

PM> Add-Migration InitialCreate

此时会自动生成InitialCreate类：

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usingSystem;usingSystem.Data.Entity.Migrations;public partial classInitialCreate : DbMigration

\{public override voidUp()

DropColumn("dbo.Student", "Email");

DropColumn("dbo.Student", "Score");

\}public override voidDown()

AddColumn("dbo.Student", "Score", c => c.Double(nullable: false));

AddColumn("dbo.Student", "Email", c => c.String(unicode: false));

2.5 执行语句：Update-Database -Verbose 更改即应用到数据库中

2.6 新增类(表)

2.6.1 新增类 City，并在DbContext类中引用实例

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public classCity

\{public string ID \{ get; set; \}public string Name \{ get; set; \}

2.6.2 执行语句

PM> Add-Migration AddCity

2.6.3 执行语句

PM> Update-Database -Verbose

查看数据，City表已经添加

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3. 参考资料

4.源码

[8f900a89c6347c561fdf2122f13be562.png]: /images/20221023/9ffb0ef3f129427b800393233a538d7d.png
[961ddebeb323a10fe0623af514929fc1.png]: /images/20221023/875449b53b374d06beb44b114479efdb.png
[40a7491271383039fe2ce7d96c3c8aca.png]: /images/20221023/a0d657776e534f73b840c41c0529d65c.png
[151bb49a2de9278548d84917a40b5584.png]: /images/20221023/81aed509cc3a42379d33efa4c3f389a2.png