Calling 'BuildServiceProvider' from application code results in copy of Singleton warning. How do I avoid this?

问题

I just pasted the 4 lines at the end from another project and it works but I get a warning.. I clearly do not understand DI well enough ... What does it want me to change ?

  public void ConfigureServices(IServiceCollection services)
        {
            if (HostingEnvironment.EnvironmentName == "Local")
            {
                services.AddHealthChecksUI()
               .AddHealthChecks()
               .AddCheck<TestWebApiControllerHealthCheck>("HomePageHealthCheck")
               .AddCheck<DatabaseHealthCheck>("DatabaseHealthCheck");
            }

        services.Configure<PwdrsSettings>(Configuration.GetSection("MySettings"));
        services.AddDbContext<PwdrsContext>(o => o.UseSqlServer(Configuration.GetConnectionString("PwdrsConnectionRoot")));

        services.AddMvc(o =>
        {
            o.Filters.Add<CustomExceptionFilter>();
        });

        services.AddCors(options =>
        {
            options.AddPolicy("CorsPolicy", b => b
                .SetIsOriginAllowed((host) => true)
                .AllowAnyMethod()
                .AllowAnyHeader()
                .AllowCredentials());
        });

        services.AddSwaggerDocument();
        services.AddHttpContextAccessor();

        services.AddAutoMapper(typeof(ObjectMapperProfile));
        services.AddTransient<IEmailSender, EmailSender>();
        services.AddScoped(typeof(IAppLogger<>), typeof(LoggerAdapter<>));
        services.AddScoped(typeof(IAsyncRepository<>), typeof(Repository<>));
        services.AddScoped<IRfReportTypeRepository, RfReportTypeRepository>();
        services.AddScoped<IRfReportRepository, RfReportRepository>();
        services.AddScoped<IRfReportLookupsService, RfReportLookupsService>();
        services.AddScoped<IRfReportService, RfReportService>();

        services.Configure<RAFLogging>(Configuration.GetSection("RAFLogging"));
        ServiceProvider serviceProvider = services.BuildServiceProvider(); //WARNING IS HERE
        IOptions<RAFLogging> RAFLogger = serviceProvider.GetRequiredService<IOptions<RAFLogging>>();
        RegisterSerilogLogger logger = new RegisterSerilogLogger(RAFLogger);
    }

回答1:

If called BuildServiceProvider() in ConfigureServices, shown warning "Calling 'BuildServiceProvider' from application code results in a additional copy of Singleton services being created"

i solved this issue:

Create another function (which passed argument is IServiceCollection) and into the function call BuildServiceProvider()

For example your code it should be:

public void ConfigureServices(IServiceCollection services)
    {
        if (HostingEnvironment.EnvironmentName == "Local")
        {
            services.AddHealthChecksUI()
           .AddHealthChecks()
           .AddCheck<TestWebApiControllerHealthCheck>("HomePageHealthCheck")
           .AddCheck<DatabaseHealthCheck>("DatabaseHealthCheck");
        }

    services.Configure<PwdrsSettings>(Configuration.GetSection("MySettings"));
    services.AddDbContext<PwdrsContext>(o => o.UseSqlServer(Configuration.GetConnectionString("PwdrsConnectionRoot")));

    services.AddMvc(o =>
    {
        o.Filters.Add<CustomExceptionFilter>();
    });

    services.AddCors(options =>
    {
        options.AddPolicy("CorsPolicy", b => b
            .SetIsOriginAllowed((host) => true)
            .AllowAnyMethod()
            .AllowAnyHeader()
            .AllowCredentials());
    });

    services.AddSwaggerDocument();
    services.AddHttpContextAccessor();

    services.AddAutoMapper(typeof(ObjectMapperProfile));
    services.AddTransient<IEmailSender, EmailSender>();
    services.AddScoped(typeof(IAppLogger<>), typeof(LoggerAdapter<>));
    services.AddScoped(typeof(IAsyncRepository<>), typeof(Repository<>));
    services.AddScoped<IRfReportTypeRepository, RfReportTypeRepository>();
    services.AddScoped<IRfReportRepository, RfReportRepository>();
    services.AddScoped<IRfReportLookupsService, RfReportLookupsService>();
    services.AddScoped<IRfReportService, RfReportService>();

    RegisterSerilogLogger logger = CreateRegisterSerilogLogger(services);
}

private RegisterSerilogLogger CreateRegisterSerilogLogger(IServiceCollection services){
        services.Configure<RAFLogging>(Configuration.GetSection("RAFLogging"));
        ServiceProvider serviceProvider = services.BuildServiceProvider(); //No warning here ))
        IOptions<RAFLogging> RAFLogger = serviceProvider.GetRequiredService<IOptions<RAFLogging>>();
        RegisterSerilogLogger logger = new RegisterSerilogLogger(RAFLogger);
    return logger;
}

Or use ApplicationServices of IApplicationBuilder. ApplicationSerivces's type is IServiceProvider.

UPDATED :

I mentioned this solution is remove warning.

I thinks correct version is to use ApplicationServices property of app, which app is IApplicationBuilder in Configure method's parameter. ApplicationServices's type is IServiceProvider.

回答2:

The ONLY purpose of calling 'BuildServiceProvider' is to get a service provider instance,

To remove this call and still be able to use IServiceProvider, change Configure method to get it as parameter:

public void Configure(IApplicationBuilder app, IHostingEnvironment env, IServiceProvider provider)

来源：https://stackoverflow.com/questions/58999401/calling-buildserviceprovider-from-application-code-results-in-copy-of-singleto