开篇语

本文主要是回顾下从项目创建到生成数据到数据库(代码优先)的全部过程。采用EFCore作为ORM框架。

本次示例环境：vs2019、net5、mysql

创建项目

本次事例代码是用过vs2019创建的ASP.NET Core Web API项目

可以通过可视化界面创建或者通过命令行创建

dotnet new webapi -o Net5ByDocker

创建实体类

安装连接MySQL数据库组件

    <PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="5.0.0" /><PackageReference Include="Pomelo.EntityFrameworkCore.MySql.Json.Newtonsoft" Version="5.0.0" />

增加实体类

    [Table("user")]public class User{public User(){Id = Guid.NewGuid().ToString();}public User(string account, string password, string creater) : this(){Account = account;Password = password;Deleted = false;SetCreater(creater);}[Key][Comment("主键")][StringLength(36)][Required]public string Id { get; private set; }[Comment("帐号")][StringLength(36)][Required]public string Account { get; private set; }[Comment("密码")][StringLength(36)][Required]public string Password { get; private set; }[Comment("余额")][Column(TypeName = "decimal(18, 2)")][Required]public decimal Money { get; set; }[Comment("是否删除")][Column(TypeName = "tinyint(1)")][Required]public bool Deleted { get; private set; }[Comment("创建人")][StringLength(20)][Required]public string Creater { get; private set; }[Comment("创建时间")][Required]public DateTime CreateTime { get; private set; }[Comment("修改人")][StringLength(20)][Required]public string Modifyer { get; private set; }[Comment("修改时间")][Required]public DateTime ModifyTime { get; private set; }public void SetCreater(string name){Creater = name;CreateTime = DateTime.Now;SetModifyer(name);}public void SetModifyer(string name){Modifyer = name;ModifyTime = DateTime.Now;}}

这种只是增加实体类类型的一种方式，可能这种看着比较乱，还可以通过OnModelCreating实现，详情看参考文档

增加数据库上下文OpenDbContext

    public class OpenDbContext : DbContext{public OpenDbContext(DbContextOptions<OpenDbContext> options): base(options){}public DbSet<User> Users { get; set; }}

Startup注入连接数据库操作

            var connection = Configuration["DbConfig:Mysql:ConnectionString"];var migrationsAssembly = IntrospectionExtensions.GetTypeInfo(typeof(Startup)).Assembly.GetName().Name;services.AddDbContext<OpenDbContext>(option => option.UseMySql(connection, ServerVersion.AutoDetect(connection), x =>{x.UseNewtonsoftJson();x.MigrationsAssembly(migrationsAssembly);}));

生成迁移文件

引用组件

<PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="5.0.5">
<PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="5.0.5">

迁移命令

add-migration Init

结果

要看下生成的迁移文件是否是自己预期的那样子，也可以在这一步就生成数据库，命令：Update-Database

数据种子

增加OpenDbSend类，添加数据种子

    public class OpenDbSend{/// <summary>/// 生成数据库以及数据种子/// </summary>/// <param name="dbContext">数据库上下文</param>/// <param name="loggerFactory">日志</param>/// <param name="retry">重试次数</param>/// <returns></returns>public static async Task SeedAsync(OpenDbContext dbContext,ILoggerFactory loggerFactory,int? retry = 0){int retryForAvailability = retry.Value;try{dbContext.Database.Migrate();//如果当前数据库不存在按照当前 model 创建，如果存在则将数据库调整到和当前 model 匹配await InitializeAsync(dbContext).ConfigureAwait(false);//if (dbContext.Database.EnsureCreated())//如果当前数据库不存在按照当前 model创建，如果存在则不管了。//  await InitializeAsync(dbContext).ConfigureAwait(false);}catch (Exception ex){if (retryForAvailability < 3){retryForAvailability++;var log = loggerFactory.CreateLogger<OpenDbSend>();log.LogError(ex.Message);await SeedAsync(dbContext, loggerFactory, retryForAvailability).ConfigureAwait(false);}}}/// <summary>/// 初始化数据/// </summary>/// <param name="context"></param>/// <returns></returns>public static async Task InitializeAsync(OpenDbContext context){if (!context.Set<User>().Any()){await context.Set<User>().AddAsync(new User("azrng", "123456", "azrng")).ConfigureAwait(false);await context.Set<User>().AddAsync(new User("张三", "123456", "azrng")).ConfigureAwait(false);}await context.SaveChangesAsync().ConfigureAwait(false);}}

设置项目启动时候调用

        public static async Task Main(string[] args){var host = CreateHostBuilder(args).Build();using (var scope = host.Services.CreateScope()){var services = scope.ServiceProvider;var loggerFactory = services.GetRequiredService<ILoggerFactory>();var _logger = loggerFactory.CreateLogger<Program>();try{var openContext = services.GetRequiredService<OpenDbContext>();await OpenDbSend.SeedAsync(openContext, loggerFactory).ConfigureAwait(false);}catch (Exception ex){_logger.LogError(ex, $"项目启动出错  {ex.Message}");}}await host.RunAsync().ConfigureAwait(false);}

生成数据库

启动项目，自动生成数据库

表结构如下

如果后期数据库字段或者结构有变动，可以再次生成迁移文件然后生成数据库

查询数据

    /// <summary>/// 用户接口/// </summary>public interface IUserService{string GetName();/// <summary>/// 查询用户信息/// </summary>/// <param name="account"></param>/// <returns></returns>Task<User> GetDetailsAsync(string account);}/// <summary>/// 用户实现/// </summary>public class UserService : IUserService{private readonly OpenDbContext _dbContext;public UserService(OpenDbContext dbContext){_dbContext = dbContext;}public string GetName(){return "AZRNG";}///<inheritdoc cref="IUserService.GetDetailsAsync(string)"/>public async Task<User> GetDetailsAsync(string account){return await _dbContext.Set<User>().FirstOrDefaultAsync(t => t.Account == account).ConfigureAwait(false);}}

一般更推荐建立指定的返回Model类，然后只查询需要的内容，不直接返回实体类

控制器方法

        /// <summary>/// 查询用户详情/// </summary>/// <param name="account"></param>/// <returns></returns>[HttpGet]public async Task<ActionResult<User>> GetDetailsAsync(string account){return await _userService.GetDetailsAsync(account).ConfigureAwait(false);}

查询结果

{"id": "e8976d0a-6ee9-4e2e-b8d8-1fe6e85b727b","account": "azrng","password": "123456","money": 0,"deleted": false,"creater": "azrng","createTime": "2021-05-09T15:48:45.730302","modifyer": "azrng","modifyTime": "2021-05-09T15:48:45.730425"
}

参考文档

实体类型：https://docs.microsoft.com/zh-cn/ef/core/modeling/entity-types?tabs=data-annotations

实体属性：https://docs.microsoft.com/zh-cn/ef/core/modeling/entity-properties?tabs=data-annotations%2Cwithout-nrt