Serilog in program class

Question

I am trying to log with Serilog in an ASP.NET Core application's Program.cs class. My current setup is as follows:

public class Program
{
    public static void Main(string[] args)
    {
        DoStuff();
        CreateWebHostBuilder(args).Build().Run();
    }
    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .ConfigureLogging((hostingContext, builder) =>
            {
                builder.AddFile(@"C:\...\log-{Date}.txt", isJson: true);
            })
            .UseStartup<Startup>();
}

I can successfully log in a Controller class by doing:

public class WebhookController : Controller
{
    readonly ILogger<WebhookController> _log;
    public WebhookController(ILogger<WebhookController> log)
    {
        _log = log;
    }
    public IActionResult Index()
    {
        _log.LogInformation("hello world");
        return View();
    }
}

However, when trying to replicate this in the program class, _log is not accessible in Main(string[] args):

public class Program
{
    readonly ILogger<Program> _log;
    public Program(ILogger<Program> log)
    {
        _log = log;
    }

    public static void Main(string[] args)
    {
        DoStuff();
        CreateWebHostBuilder(args).Build().Run();
    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .ConfigureLogging((hostingContext, builder) =>
            {
                builder.AddFile(@"C:\...\log-{Date}.txt", isJson: true);
            })
            .UseStartup<Startup>();
}

How can I configure Serilog to log in the program class?

Answer 1

When the web host is built, the IWebHost exposes IWebHost.Services Property

public IServiceProvider Services { get; }

which can be used to resolve the desired dependencies.

public class Program {

    public static void Main(string[] args) {
        var webHost = CreateWebHostBuilder(args).Build();
        var services = webHost.Services;

        var log = services.GetService<ILogger<Program>>();

        DoStuff(log);

        webHost.Run();
    }

    static void DoStuff(ILogger<Program> log) {
        //...
    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .ConfigureLogging((hostingContext, builder) =>
            {
                builder.AddFile(@"C:\...\log-{Date}.txt", isJson: true);
            })
            .UseStartup<Startup>();
}

Remember to include using Microsoft.Extensions.DependencyInjection; in order to have access to the .GetService<T>() extension method on IServiceProvider.