.Net Entity Framework连接MySql

Posted 2021-10-14 シ゛甜虾

一、Nuget安装 Entity Framework

 二、基本代码编写

创建Models文件夹，然后在创建Table文件夹，在Table中创建表的实体类

 然后在创建DataContext类，内容如下

using EdgeService.DbService.Models.Table;
using Microsoft.EntityFrameworkCore;

namespace EdgeService.DbService.Models
{
    public class DataContext : DbContext
    {
        public DataContext(DbContextOptions<DataContext> options)
            : base(options)
        {
        }

        public DbSet<DeviceInfoTable> DeviceInfoTables { get; set; }
        public DbSet<HeartbeatTableDto> HeartbeatTableDtos { get; set; }
        public DbSet<SettingMessageDto> SettingMessageDtos { get; set; }
        public DbSet<SettingTableDto> SettingTableDtos { get; set; }
        public DbSet<SetWorkmodeTableDto> SetWorkmodeTableDtos { get; set; }
    }
}

构建迁移出现下面错误

Unable to create an object of type 'DataContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

创建SchoolContextFactory类

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Design;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EdgeService.DbService.Models
{
    public class SchoolContextFactory : IDesignTimeDbContextFactory<DataContext>
    {
        // IConfiguration Configuration { get; } //使用Configuration 获取不到GetConnectionString("SchoolContext")。不能用
        public DataContext CreateDbContext(string[] args)
        {
            var optionsBuilder = new DbContextOptionsBuilder<DataContext>();
            //   optionsBuilder.UseSqlServer(Configuration.GetConnectionString("SchoolContext"));
            string ConnectionString = "server=127.0.0.1;uid=root;pwd=密码;database=edgedb";
            optionsBuilder.Usemysql(ConnectionString, new MySqlServerVersion(new Version(5, 7, 0)));
            return new DataContext(optionsBuilder.Options);
        }

    }
}

三、测试

打开程序包管理控制台

输入

Add-Migration init

成功之后或多出来一个Migrations文件夹和数据库升级脚本

执行Update-database就会创建数据库和表

控制台内容

 

四、自动迁移

在构造函数中添加

public DataContext(DbContextOptions<DataContext> options)
    : base(options)
{

    if (Database.GetPendingMigrations().Any())
    {
        Database.Migrate(); //执行迁移
    }
    //Migrate()方法使用前需在程序包管理控制台执行Add - migration迁移命令。之后程序每次启动，GetPendingMigrations()都会去检测是否有待迁移内容，有的话，自动应用迁移。

    //如果成功创建了数据库，则返回true
    //DbContext.Database.EnsureCreated()
    //此方法不需要先执行Add - migration迁移命令，如果数据库不存在，则自动创建并返回true。
    //如果已经创建了数据库后，又改动了实体Model和之前的库存在冲突，要注意删库让它自动重建，否则会报错。
}

DataContext在实例化是就会进行自动迁移了

五、索引列自动增长

配置成Identity才可以自增，配置成None是不行的哦

[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }

配置成Identity后AI才会被选中 

六、DataContext的使用方式

注入到ServiceCollection中

var serviceProvider = new ServiceCollection()
                    .AddSingleton<IDataCache, DataCache>()
                    .AddDbContext< DataContext > (optionsBuilder =>
                    optionsBuilder.UseMySql(ConnectionString, new MySqlServerVersion(new Version(5, 7, 0))))
                        .AddSingleton<LogLibrary.ILogger, Log4netLogger>()
                    .BuildServiceProvider();

注入到builder.Services

var logger = SingleService.Services.GetService<LogLibrary.ILogger>();
if (logger != null)
{
    logger.Debug(typeof(WebApiService), "WebApiService InitAndStart");
}

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
builder.Services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new() { Title = "EdgeService.WebApi", Version = "v1" });
});

builder.Host.ConfigureHostConfiguration(configHost =>
{
    configHost.AddJsonFile("hostsettings.json", optional: true);
});

string ConnectionString = "server=127.0.0.1;uid=root;pwd=密码;database=edgedb";

builder.Services.AddDbContext<DataContext>(optionsBuilder =>
optionsBuilder.UseMySql(ConnectionString, new MySqlServerVersion(new Version(5, 7, 0))));

创建新的实例

string ConnectionString = "server=127.0.0.1;uid=root;pwd=密码;database=edgedb";
DbContextOptions<DataContext> dbContextOption = new DbContextOptions<DataContext>();
DbContextOptionsBuilder<DataContext> dbContextOptionBuilder = new DbContextOptionsBuilder<DataContext>(dbContextOption);
DataContext _dbContext = new DataContext(dbContextOptionBuilder.UseMySql(ConnectionString, new MySqlServerVersion(new Version(5, 7, 0))).Options);