c# - 从 ASP.NET Core 2.0 中的 json 文件进行数据库播种的正确位置是什么？

Question

在我的 Core 1.0 应用程序中，Startup ctor 将几个额外的 json 文件加载到配置中...

public Startup(IHostingEnvironment env) {
    Environment = env;

    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json")
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json")
        .AddJsonFile($"activityGroups.{env.EnvironmentName}.json")
        .AddEnvironmentVariables();

    Configuration = builder.Build();
}

然后在 ConfigureServices 中，我将这些数据从配置中抓取到强类型列表中......

public void ConfigureServices(IServiceCollection services) {
    services.AddDbContext<Models.DbContext>(
        options => options.UseSqlServer(
            Configuration["Data:DefaultConnection:ConnectionString"]
        )
    );

    services.AddScoped<Repository>();
    services.AddTransient<DbSeed>();
    services.AddOptions();

    services.Configure<List<Models.Task>>(Configuration.GetSection("ActivityGroups"));
}

然后，在 Configure 中，强类型列表被注入(inject)并用于 db init..

public void Configure(
    IApplicationBuilder app,
    DbSeed seed,
    ILoggerFactory logging,
    IOptions<List<ActivityGroup>> activityGroupConfig
    ) {

    app.UseAuthentication();
    app.UseMvc();

    bool seedDb;
    bool.TryParse(Configuration.GetSection("SeedDb").Value, out seedDb);
    if (seedDb) {
        seed.EnsureSeeded(activityGroupConfig.Value);
    }
}

然而...

In 2.0 projects, move the SeedData.Initialize call to the Main method of Program.cs...

As of 2.0, it's bad practice to do anything in BuildWebHost except build and configure the web host. [configure web host includes data seeding?] Anything that's about running the application should be handled outside of BuildWebHost — typically in the Main method of Program.cs.
https://learn.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/#move-database-initialization-code

但是，在"new"Main(string[] args) 中，我们无权访问 dbcontext(直到 Startup.ConfigureServices)。即使在 MS 文档中的 SeedData.Initialize(services); 调用中，SeedData 将如何访问直到稍后在配置服务中才定义的连接字符串？

The adoption of this new 2.0 pattern is highly recommended and is required for product features like Entity Framework (EF) Core Migrations to work.
https://learn.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/#update-main-method-in-programcs

我一直在谷歌搜索和挖掘文档和 samples (例如带有硬编码值的种子)没有清楚地了解期望或推荐的设计(除了，“不要做你以前做过的事”。)

这里有人更熟悉或更有经验如何在 ASP.NET Core 2.0 中从磁盘上的 json 进行数据库播种吗？

Answer 1

因此，在 this SO question 的帮助下，我得到了从 Program.cs 中获取服务的要点

public class Program {
    public static void Main(string[] args) {
        var host = BuildWebHost(args);

        using (var scope = host.Services.CreateScope())
        {
            var services = scope.ServiceProvider;
            var logger = services.GetRequiredService<ILoggerFactory>();

            var ctx = services.GetRequiredService<DataContext>();
            // Now I can access the DbContext, create Repository, SeedData, etc!

现在，问题在于试图找出如何从 appsettings.json 访问值，新的 SO 问题 here .