c# - 从应用程序代码调用“BuildServiceProvider”会导致单例警告的副本。我该如何避免这种情况?
问题描述
我刚刚从另一个项目的最后粘贴了 4 行,它可以工作,但我收到警告.. 我显然对 DI 理解不够好......它想让我改变什么?
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);
}
解决方案
如果在 ConfigureServices 中调用 BuildServiceProvider(),则会显示警告“从应用程序代码调用 'BuildServiceProvider' 会导致创建单例服务的附加副本”
我解决了这个问题:
创建另一个函数(传递的参数是 IServiceCollection)并进入函数调用 BuildServiceProvider()
例如你的代码应该是:
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;
}
或者使用 IApplicationBuilder 的 ApplicationServices。ApplicationServices 的类型是 IServiceProvider。
我提到此解决方案仅用于删除警告。
调用 BuildServiceProvider 会创建第二个容器,该容器可以创建撕裂的单例并导致跨多个容器引用对象图。
2021 年 1 月 24 日更新
我读了亚当弗里曼的Pro ASP.NET Core 3 8th
书。Adam Freeman在第 157 页app.ApplicationServices
中services.BuildServiceProvider()
用于此目的,该应用程序是该方法位于 Startup.cs 中的 Configure 方法的参数
我认为正确的版本是使用应用程序的 ApplicationServices 属性,该应用程序是配置方法参数中的 IApplicationBuilder。ApplicationServices 的类型是 IServiceProvider。
Adam Freeman 的 Pro ASP.NET Core 3 第 8 本书:Pro ASP.NET Core 3
Adam Freeman 的示例项目:SportStore 项目的 Startup.cs,SportStore 项目的 SeedData.cs
微软关于 DI 的建议:ASP.NET Core 中的依赖注入
Stackoverflow 中类似问题的答案:https ://stackoverflow.com/a/56058498/8810311 , https://stackoverflow.com/a/56278027/8810311