public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<ISelfServiceConfigLoad, SelfServiceConfigLoader>();
    var sp = services.BuildServiceProvider();
    var configservice = sp.GetServices<ISelfServiceConfigLoad>();
    services.AddSingleton<IExtractor, ConfigExtractor>( sp =>
    {
        var con = sp.GetRequiredService<ISelfServiceConfigLoad>();
        var config = con.Load();
        return new ConfigExtractor(config.Result);
    });
    services.AddSingleton<IProcessor<EventMessage>, SelfServiceProcessor>();          
    services.AddTransient<ISolrPush, SolrDataPush>();
    services.AddSingleton<IAPICaller<string, string>, ApiRestCaller<string, string>>();
    services.AddSingleton<IDataRetriever<SelfServiceApiRequest, IDictionary<string, object>>, SelfServiceDataRetriever>();
}

您可以使用IApplicationBuilder实例以这种方式注入依赖项

public void Configure(IApplicationBuilder app)
{
    //---------- Your code

    using (var serviceScope = app.ApplicationServices.GetRequiredService<IServiceScopeFactory>().CreateScope())
    {
        var resultLogic = serviceScope.ServiceProvider.GetService<IResultLogic>();
        resultLogic.YourMethod();
    }

    //---------- Your code
}

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    services.AddDbContext<ConfigurationRepository>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("SqlConnectionString")));

    services.AddScoped<IConfigurationBL, ConfigurationBL>();
    services.AddScoped<IConfigurationRepository, ConfigurationRepository>();
}

我知道这是一个老问题，但我很惊讶，一个相当明显和恶心的黑客没有在这里。

您可以利用定义自己的ctor函数的能力，在定义服务时从服务中获取必要的值……显然，每次请求服务时都会运行此服务，除非您在利用ctor的第一个构造中显式地删除/清除并重新添加此服务的定义。

这种方法的优点是不需要您在服务配置期间构建或使用服务树。您仍然在定义如何配置服务。

public void ConfigureServices(IServiceCollection services)
{
    //Prey this doesn't get GC'd or promote to a static class var
    string? somevalue = null;

    services.AddSingleton<IServiceINeedToUse, ServiceINeedToUse>(scope => {
         //create service you need
         var service = new ServiceINeedToUse(scope.GetService<IDependantService>())
         //get the values you need
         somevalue = somevalue ?? service.MyDirtyHack();
         //return the instance
         return service;
    });
    services.AddTransient<IOtherService, OtherService>(scope => {
         //Explicitly ensuring the ctor function above is called, and also showcasing why this is an anti-pattern.
         scope.GetService<IServiceINeedToUse>();
         //TODO: Clean up both the IServiceINeedToUse and IOtherService configuration here, then somehow rebuild the service tree.
         //Wow!
         return new OtherService(somevalue);
    });
}

修复这个模式的方法是让OtherService显式依赖于IServiceINeedToUse，而不是隐式依赖于它或它的方法的返回值…或者以其他方式显式地解决依赖关系。

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<ISelfServiceConfigLoad, SelfServiceConfigLoader>();
    var sp = services.BuildServiceProvider();
    var configservice = sp.GetServices<ISelfServiceConfigLoad>();
    services.AddSingleton<IExtractor, ConfigExtractor>( sp =>
    {
        var con = sp.GetRequiredService<ISelfServiceConfigLoad>();
        var config = con.Load();
        return new ConfigExtractor(config.Result);
    });
    services.AddSingleton<IProcessor<EventMessage>, SelfServiceProcessor>();          
    services.AddTransient<ISolrPush, SolrDataPush>();
    services.AddSingleton<IAPICaller<string, string>, ApiRestCaller<string, string>>();
    services.AddSingleton<IDataRetriever<SelfServiceApiRequest, IDictionary<string, object>>, SelfServiceDataRetriever>();
}

手动解析实例需要使用IServiceProvider接口:

在启动时解决依赖关系。ConfigureServices

public void ConfigureServices(IServiceCollection services)
{
    services.AddTransient<IMyService, MyService>();

    var serviceProvider = services.BuildServiceProvider();
    var service = serviceProvider.GetService<IMyService>();
}

解决启动中的依赖关系。配置

public void Configure(
    IApplicationBuilder application,
    IServiceProvider serviceProvider)
{
    // By type.
    var service1 = (MyService)serviceProvider.GetService(typeof(MyService));

    // Using extension method.
    var service2 = serviceProvider.GetService<MyService>();

    // ...
}

解决启动中的依赖关系。在ASP中配置。NET Core 3

public void Configure(
    IApplicationBuilder application,
    IWebHostEnvironment webHostEnvironment)
{
    application.ApplicationServices.GetService<MyService>();
}

使用运行时注入的服务

有些类型可以作为方法参数注入:

public class Startup
{
    public Startup(
        IHostingEnvironment hostingEnvironment,
        ILoggerFactory loggerFactory)
    {
    }

    public void ConfigureServices(
        IServiceCollection services)
    {
    }

    public void Configure(
        IApplicationBuilder application,
        IHostingEnvironment hostingEnvironment,
        IServiceProvider serviceProvider,
        ILoggerFactory loggerfactory,
        IApplicationLifetime applicationLifetime)
    {
    }
}

解决控制器动作中的依赖关系

[HttpGet("/some-action")]
public string SomeAction([FromServices] IMyService myService) => "Hello";