示例：EntityframeWorkCore应用MySql做数据迁移

本文主要是介绍示例：EntityframeWorkCore应用MySql做数据迁移，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

一、目的：应用EF Core和MySql数据库了解做数据库迁移的步骤

 

二、环境：VS2019、.NetCore 2.2、Mysql 8.0.15、Win10

 

三、步骤：

 

1、新建类库(core)并创建DataContext

   public class DataContext : DbContext{protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder){optionsBuilder.UseMySQL("server=localhost;userid=****;pwd=****;port=****;database=****;sslmode=none;");}public  DbSet<City> Citys { get; set; }    }public class City{public int Id { get; set; }public string Name { get; set; }public DateTime CDate { get; set; }}

 

2、安装Nuget包：MySql.Data.EntityFrameworkCore

 

3、安装Nuget包：MySql.Data.EntityFrameworkCore.Design

 

4、安装Nuget包：Microsoft.EntityFrameworkCore.Tools

 

5、在程序包管理控制台页面输入:get-help entityframework 查看所有可执行的命令

 

程序包管理器：工具->Nuget包管理系

 

Cmdlet                      Description
        --------------------------  ---------------------------------------------------
        Add-Migration               Adds a new migration.

        Drop-Database               Drops the database.

        Get-DbContext               Gets information about a DbContext type.

        Remove-Migration            Removes the last migration.

        Scaffold-DbContext          Scaffolds a DbContext and entity types for a database.

        Script-Migration            Generates a SQL script from migrations.

        Update-Database             Updates the database to a specified migration.

6、执行命令一：add-migration +迁移名称

  输出：没有报错，并且生成文件夹“Migrations”和如下文件，表示执行成功

    public partial class init : Migration{protected override void Up(MigrationBuilder migrationBuilder){migrationBuilder.CreateTable(name: "Citys",columns: table => new{Id = table.Column<int>(nullable: false).Annotation("MySQL:AutoIncrement", true),Name = table.Column<string>(nullable: true)},constraints: table =>{table.PrimaryKey("PK_Citys", x => x.Id);});}protected override void Down(MigrationBuilder migrationBuilder){migrationBuilder.DropTable(name: "Citys");}}

7、执行命令二：update-datebase

输出：Done 并且数据库生成数据表或执行更改，表示执行成功

 

注：同时也可以应用命令Script-Migration可以生成数据库Sql脚本，在数据库执行

  IF EXISTS(SELECT 1 FROM information_schema.tables WHERE table_name = '
__EFMigrationsHistory' AND table_schema = DATABASE()) 
BEGIN
CREATE TABLE `__EFMigrationsHistory` (`MigrationId` varchar(150) NOT NULL,`ProductVersion` varchar(32) NOT NULL,PRIMARY KEY (`MigrationId`)
);END;CREATE TABLE `Citys` (`Id` int NOT NULL AUTO_INCREMENT,`Name` text NULL,PRIMARY KEY (`Id`)
);INSERT INTO `__EFMigrationsHistory` (`MigrationId`, `ProductVersion`)
VALUES ('20190513100712_init', '2.2.4-servicing-10062');ALTER TABLE `Citys` ADD `CDate` datetime NOT NULL DEFAULT '0001-01-01 00:00:00.000000';INSERT INTO `__EFMigrationsHistory` (`MigrationId`, `ProductVersion`)
VALUES ('20190513101011_changecity', '2.2.4-servicing-10062');INSERT INTO `Citys` (`Id`, `CDate`, `Name`)
VALUES (1, '0001-01-01 00:00:00.000000', '成都');INSERT INTO `Citys` (`Id`, `CDate`, `Name`)
VALUES (5, '0001-01-01 00:00:00.000000', '北京');INSERT INTO `__EFMigrationsHistory` (`MigrationId`, `ProductVersion`)
VALUES ('20190513104003_changehasdata', '2.2.4-servicing-10062');

常见问题：

1、如果报“Table 'test.__efmigrationshistory' doesn't exist”表不存在错误，可以手动执行一次初始化sql语句

 CREATE TABLE `__EFMigrationsHistory`
 (
 `MigrationId` nvarchar(150) NOT NULL,
 `ProductVersion` nvarchar(32) NOT NULL,
PRIMARY KEY(`MigrationId`)
 );

2、如果报“Value cannot be null. Parameter name: input ”则是少安装Nuget包，如：Microsoft.EntityFrameworkCore.Tools

 

以上就是EF Core 针对MySql数据库做迁移的方法和步骤

示例地址： https://github.com/HeBianGu/.NetCore-LearnDemo.git

 

 

 

 

这篇关于示例：EntityframeWorkCore应用MySql做数据迁移的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！

---