asp.net - 从 ASP.NET Core 2.2 迁移到 3.1 时 services.BuildServiceProvider(在ConfigureServices 中)的替代代码

Question

我有模块化的 ASP.NET Core 应用程序。回到 .NET Core 1.1 时代，我在 public void ConfigureServices(IServiceCollection services) 方法中构建服务(AddScoped、AddSingleton ...)像这样:

public void ConfigureServices(IServiceCollection services)
{
    //...
    var sp = services.BuildServiceProvider();
    GlobalConfiguration.ModuleInitializers = sp.GetServices<IModuleInitializer>();
    foreach (var moduleInitializer in GlobalConfiguration.ModuleInitializers)
        moduleInitializer.ConfigureServices(services, this.Configuration, this.Environment);
}

每个模块(库)都有自己的类，它实现“IModuleInitializer”并注册服务:

public class ModuleInitializer : IModuleInitializer
{
    public void ConfigureServices(IServiceCollection serviceCollection, IConfiguration configuration, IHostingEnvironment environment)
    {
        serviceCollection.AddScoped<....>();
        serviceCollection.AddScoped<...>();
        ...

从 .NET Core 2.2 迁移到 3.1 时，我收到警告:

Calling 'BuildServiceProvider' from application code results in an additional copy of singleton services being created. Consider alternatives such as dependency injecting services as parameters to 'Configure'

我已经了解了这意味着什么，问题出在哪里......，但是我在如何在模块设计应用程序中正确配置服务方面遇到了问题。

我还需要从互联网获取有关模块的信息。我的问题是这种方法是否好，或者有更好/推荐的吗？

public Startup(IConfiguration configuration)
{
    Configuration = configuration;    //From https://learn.microsoft.com/en-us/aspnet/core/fundamentals/startup?view=aspnetcore-3.1
}

public void ConfigureServices(IServiceCollection services)
{
    ...

    var serverSett = this.Configuration.GetSection("Server").Get<ServerSettings>();
    string[] allowedModules;
    using (var httpClientHandler = new HttpClientHandler())
    {
        allowedModules = //Get allowed modules from web
    }
    if (allowedModules.Any(t => t == "Shopping");
        services.AddShopping();    //Extension method in Shopping library which register own services.
    if (allowedModules.Any(t => t == "Offer");
        services.AddOffer();    //Extension method in Offer library which register own services.
}

Answer 1

使用 DI 来设置 DI 有点问题，而且肯定会出现问题。

为什么不直接使用一些反射来获取 IModuleInitializers。

var moduleInitializers = typeof(MyAssembly).GetTypeInfo().Assembly
    .GetTypes()
    .Where(type =>
        !type.GetTypeInfo().IsAbstract &&
        typeof(IModuleInitializer).IsAssignableFrom(type))
    .Select(type => Activator.CreateInstance(type))
    .Cast<IModuleInitializer>()
    .ToArray();

foreach (var moduleInitializer in moduleInitializers)
    moduleInitializer.ConfigureServices(services, this.Configuration, this.Environment);

关于你的第二个问题我无法给你建议。但我会质疑动态设置应用程序的必要性，除非您确实需要这样做。