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
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创建实体类

安装组件

    <PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="5.0.0" />
    <PackageReference Include="Pomelo.EntityFrameworkCore.MySql.Json.Newtonsoft" Version="5.0.0" />
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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;
        }
    }
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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; }
    }
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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);
            }));
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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">
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迁移命令

add-migration Init
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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);
        }
    }
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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);        }
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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);        }    }
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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);        }
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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"}
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