c# - 如何在 ASP.NET Core 5.0 中的 Startup.cs 的 ConfigureServices 方法中执行日志记录

Question

记录器的构造函数注入(inject) Startup在早期版本的 ASP.NET Core 中工作，因为为 Web 主机创建了一个单独的 DI 容器。目前只为通用主机创建了一个容器，参见 breaking change announcement .

启动文件

public class Startup
{
    /// <summary> The configuration. </summary>
    public IConfiguration Configuration { get; }
    
    /// <summary> The web host environment. </summary>
    public IWebHostEnvironment WebHostEnvironment { get; }

    public Startup(IConfiguration configuration, IWebHostEnvironment webHostEnvironment)
    {
        Configuration = configuration;
        WebHostEnvironment = webHostEnvironment;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddServices(Configuration);    // This is a custom method, that adds multiple services to the container.
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILogger<Startup> logger) =>
    app.UseComponents(env, Configuration, logger);
}

现在按照 MSDN ，我已经修改了我的 Startup.cs 如下:

public class Startup
{
    /// <summary> The configuration. </summary>
    public IConfiguration Configuration { get; }
    
    public ILogger<Startup> Logger { get; set; }

    /// <summary> The web host environment. </summary>
    public IWebHostEnvironment WebHostEnvironment { get; }

    public Startup(IConfiguration configuration, IWebHostEnvironment webHostEnvironment)
    {
        Configuration = configuration;
        WebHostEnvironment = webHostEnvironment;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddSingleton((container) =>
        {
            var logger = container.GetRequiredService<ILogger<MyService>>();
            return new Startup(Configuration, WebHostEnvironment) { Logger = logger };
        });    // I know this is incorrect, but that my question- how do I correctly access logger in here?
        services.AddServices(Configuration, Logger);    // Logger => null
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILogger<Startup> logger) =>
    app.UseComponents(env, Configuration, logger);
}

启动扩展.ConfigureServices.cs

public static partial class StartupExtension
{
    #region Internal Method
    /// <summary> Adds all the services required by the DemoUsageApp. </summary>
    /// <param name="services">The services, <see cref="IServiceCollection"/>.</param>
    /// <param name="configuration">The configuration, <see cref="IConfiguration"/>.</param>
    /// <param name="logger">The logger, <see cref="ILogger{Startup}"/>.</param>
    /// <returns></returns>
    internal static IServiceCollection AddServices(this IServiceCollection services, IConfiguration configuration, ILogger logger)
    {
        services.AddDotNetCoreServices(configuration, logger);
        services.AddCrossCuttingServices(configuration, logger);

        return services;
    }
    #endregion Internal Method

    #region Private Methods
    /// <summary> Adds .NET Core services. </summary>
    /// <param name="services">The services, <see cref="IServiceCollection"/>.</param>
    /// <param name="configuration">The configuration, <see cref="IConfiguration"/>.</param>
    /// <param name="logger">The logger, <see cref="ILogger{Startup}"/>.</param>
    /// <returns></returns>
    private static IServiceCollection AddDotNetCoreServices(this IServiceCollection services, IConfiguration configuration, ILogger logger)
    {
        logger.LogInformation("----  Adding .NET Core components  ----");

        services.AddMvc();
        services.AddControllers();

        logger.LogInformation("----  Successfully added .NET Core components  ----");

        return services;
    }

    /// <summary> Adds Cross-Cutting services. </summary>
    /// <param name="services">The services, <see cref="IServiceCollection"/>.</param>
    /// <param name="configuration">The configuration, <see cref="IConfiguration"/>.</param>
    /// <param name="logger">The logger, <see cref="ILogger{Startup}"/>.</param>
    /// <returns></returns>
    private static IServiceCollection AddCrossCuttingServices(this IServiceCollection services, IConfiguration configuration, ILogger logger)
    {
        logger.LogInformation("----  Adding Cross-Cutting components  ----");

        services.AddSql(configuration, logger);    //This is a extension methods, that adds Sql services (which are also completely custom) to the application.

        logger.LogInformation("----  Successfully added Cross-Cutting components  ----");

        return services;
    }
    #endregion Private Methods
}

问题- 如何在 Startup.cs 的 ConfigureServices 方法中访问 Logger，以便我可以将其传递给向容器添加自定义服务的其他自定义扩展方法？
注意:为 Microsoft 和 Serilog Logger 请求的解决方案(可选)。
更新 1:正如@MathewBeck 在他的第二条评论中指出的那样，我已经有了以下结构 Program.cs :

public class Program
{
    #region Public Methods
    /// <summary> Main method, the entry-point of the application. </summary>
    /// <param name="args">The args <see cref="string[]"/></param>
    public static void Main(string[] args)
    {
        var host = CreateHostBuilder(args).Build();
        var logger = host.Services.GetRequiredService<ILogger<Program>>();
        logger.LogInformation("Host created.");

        host.Run();
    }

    /// <summary> Creates the host builder. </summary>
    /// <param name="args">The args <see cref="string[]"/></param>
    /// <returns></returns>
    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            //.ConfigureLogging(loggingBuilder =>
            //{
            //    loggingBuilder.ClearProviders();
            //    loggingBuilder.AddConsole();
            //    loggingBuilder.AddDebug();
            //    loggingBuilder.AddEventLog();
            //    loggingBuilder.AddEventSourceLogger();
            //})
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
                webBuilder.UseConfiguration(GetConfiguration());
            });
    #endregion Public Methods

    #region Private Methods
    /// <summary> Gets the configuration. </summary>
    /// <returns></returns>
    private static IConfiguration GetConfiguration()
    {
        var env = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Development";
        var builder = new ConfigurationBuilder()
            .AddJsonFile("appsettings.json", true, true)
            .AddJsonFile($"appsettings.{env}.json", true, true);

        return builder.Build();
    }
    #endregion Private Methods
} 

Answer 1

如果您使用 NLog，登录 startup.cs 的最简单方法是添加私有(private)属性。

private readonly NLog.ILogger _log;

然后在你的构造函数中使用

_log = NLog.LogManager.GetCurrentClassLogger();