无法解析类型“Microsoft.Extensions.Logging.ILogger`1[WebApplication1.Startup]”的服务答案

【问题标题】：Unable to resolve service for type 'Microsoft.Extensions.Logging.ILogger`1[WebApplication1.Startup]'无法解析类型“Microsoft.Extensions.Logging.ILogger`1[WebApplication1.Startup]”的服务
【发布时间】：2019-07-01 10:13:38
【问题描述】：

我在 Visual Studio 2019 Preview 2.2 中使用默认模板创建了一个 ASP.NET Core 3.0 Web 应用程序，并尝试在 Startup 中注入一个 ILogger：

namespace WebApplication1
{
    public class Startup
    {
        private readonly ILogger _logger;

        public Startup(IConfiguration configuration, ILogger<Startup> logger)
        {
            Configuration = configuration;
            _logger = logger;
        }
        // ...
    }
}

在 Program.cs 中我还调用了 ConfigureLogging() 方法：

namespace WebApplication1
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureLogging((hostingContext, logging) =>
                {
                    logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
                    logging.ClearProviders();
                    logging.AddConsole();
                })
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }
}

它在 ASP.NET Core 2.x 中有效，但在 ASP.NET Core 3 中失败并出现以下错误：

System.InvalidOperationException: Unable to resolve service for type 'Microsoft.Extensions.Logging.ILogger`1[WebApplication1.Startup]' while attempting to activate 'WebApplication1.Startup'.
   at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.ConstructorMatcher.CreateInstance(IServiceProvider provider)
   at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.CreateInstance(IServiceProvider provider, Type instanceType, Object[] parameters)
   at Microsoft.AspNetCore.Hosting.Internal.GenericWebHostBuilder.UseStartup(Type startupType, HostBuilderContext context, IServiceCollection services)
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Hosting.Internal.GenericWebHostBuilder.<>c__DisplayClass13_0.<UseStartup>b__2(IApplicationBuilder app)
   at Microsoft.AspNetCore.Server.IIS.Core.IISServerSetupFilter.<>c__DisplayClass2_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.HostFilteringStartupFilter.<>c__DisplayClass0_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.Internal.GenericWebHostService.StartAsync(CancellationToken cancellationToken)

知道是什么导致了这种行为吗？

在默认“Web 应用程序”模板的完整 Program.cs 和 Startup.cs 文件下方，仅添加了日志记录。

程序.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace WebApplication1
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureLogging((hostingContext, logging) =>
                {
                    logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
                    logging.ClearProviders();
                    logging.AddConsole();
                })
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }
}

Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace WebApplication1
{
    public class Startup
    {
        private readonly ILogger _logger;
        public Startup(IConfiguration configuration, ILogger<Startup> logger)
        {
            Configuration = configuration;
            _logger = logger;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.Configure<CookiePolicyOptions>(options =>
            {
                // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
            });

            //services.AddTransient(typeof(ILogger<>), (typeof(Logger<>)));

            services.AddMvc()
                .AddNewtonsoftJson();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRouting(routes =>
            {
                routes.MapApplication();
            });

            app.UseCookiePolicy();

            app.UseAuthorization();
        }
    }
}

【问题讨论】：

我认为您应该直接使用 ILoggerFactory 而不是 ILogger？
ILoggerFactory 出现相同类型的错误。
你打电话给WebHostBuilder().ConfigureLogging(...)吗？
我没有，但我认为这对本次测试来说没问题，它应该使用默认的日志记录设置对吗？
你能分享你的Startup 或 Program.cs 吗？

标签： c# asp.net-core razor-pages visual-studio-2019 asp.net-core-3.0

【解决方案1】：

很遗憾，在 ASP.NET Core 3.0 中无法再将ILogger 注入 Startup.cs。

https://docs.microsoft.com/en-us/azure/azure-monitor/app/ilogger#capture-ilogger-logs-from-startupcs-and-programcs-in-aspnet-core-apps

注意

在 ASP.NET Core 3.0 及更高版本中，不再可以注入 Startup.cs 和 Program.cs 中的 ILogger。看 https://github.com/aspnet/Announcements/issues/353了解更多详情。

编辑：在 Startup.cs 的 Configure 方法中进行日志记录的一种可能方式是：

            using (var logScope = app.ApplicationServices.CreateScope())
            {
                var logger = logScope.ServiceProvider.GetService<ILogger<Startup>>();
                logger.LogInformation("Some information");
            }

【讨论】：

那么...我们从启动时向需要 ILogger 的服务传递什么？
@BrainSlugs83 我在 Configure() 方法中添加了一种方法。

【解决方案2】：

如果你想在调用 Configure() 之后记录事情，你仍然可以通过方法注入注入 ILogger（与首选的构造函数注入相反：

public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILogger<TStartup> logger)
{
     _logger = logger;
     ...
}

【讨论】：

【解决方案3】：

这可以通过手动注册ILogger 以使用 Startup 类作为类型来解决。

例子：

public void ConfigureServices(IServiceCollection services)
{
    // Normal AddLogging
    services.AddLogging();

    // Additional code to register the ILogger as a ILogger<T> where T is the Startup class
    services.AddSingleton(typeof(ILogger), typeof(Logger<Startup>)); 
  
    // ...
}

【讨论】：

只有这个解决方案适用于 .NET Core 3.1

【解决方案4】：

从 dotnet 3.0 开始，Web 应用程序使用 IHostBuilder 而不是 IWebHostBuilder。 所以不能再直接在 Startup 类中注入 ILogger 了。

https://github.com/dotnet/docs/issues/14900

您可以通过在构建器中直接为 Startup 类创建记录器来解决此问题。

Program.cs

public class Program
{
    public static void Main(string[] args)
    {
        CreateHostBuilder(args)
                .Build()
                .Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args)
    {
        return Host.CreateDefaultBuilder(args)
                   .ConfigureLogging(AppLoggingConfiguration)
                   .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); })
                   .UseWindowsService();
    }

    public static void AppLoggingConfiguration(ILoggingBuilder loggingBuilder)
    {
        loggingBuilder.ClearProviders();
        loggingBuilder.AddDebug();
        loggingBuilder.AddConsole();
        loggingBuilder.AddEventLog(new EventLogSettings
                                   {
                                           SourceName = "MySourceName",
                                           LogName = "Application",
                                   });
    }
}

Startup.cs

public class Startup
{
    private readonly ILogger<Startup> _logger;

    public Startup(IConfiguration configuration)
    {
        this.Configuration = configuration;
        var lf = LoggerFactory.Create(Program.AppLoggingConfiguration);
        _logger = lf.CreateLogger<Startup>();
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
                    
        /// ...    
        _logger.LogInformation("Hello startup");
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
      /// ...    
    }
}

【讨论】：

【解决方案5】：

此问题与IHostBuilder 有关。

对于临时解决方法，我建议您尝试使用 IWebHost 替换 IHostBuilder。

像改变你的 Program.cs

public class Program
{
    public static void Main(string[] args)
    {           
        BuildWebHost(args).Run();
    }
    public static IWebHost BuildWebHost(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .ConfigureLogging(logging =>
                {
                    logging.ClearProviders();
                    logging.AddConsole();
                })
                .Build();      
}

【讨论】：

虽然这确实允许应用程序启动，但您最终会遇到错误“尝试激活 '' 时无法解析类型 'Microsoft.Extensions.Logging.ILogger' 的服务”它不能解决问题。

【解决方案6】：

你有没有使用 ServiceCollection 来注册 Logger！它应该在这里。

serviceProvider.AddTransient(typeof(ILogger<>), (typeof(Logger<>));

或者你说，这是 Program.cs 的示例

public class Program  
{  
    public static void Main(string[] args)  
    {  
        BuildWebHost(args).Run();  
    }  

    public static IWebHost BuildWebHost(string[] args) =>  
        WebHost.CreateDefaultBuilder(args)  
            .ConfigureLogging(logging => logging.SetMinimumLevel(LogLevel.Warning))  
            .UseStartup<Startup>()  
            .Build();  
}

【讨论】：

感谢您的回答，但它也不起作用。