How to log to a file without using third party logger in .Net Core 3 ASP.NET MVC?

There are several libraries available in the market to archive this, But I am using the Serilog.AspNetCore and Serilog.Sinks.RollingFile packages in My Web API project which used .Net Core 3.0.

First You have to configure the Program class as below.

public static void Main(string[] args)
        {
            Log.Logger = new LoggerConfiguration()
                                .WriteTo.RollingFile("Log_{Date}.txt")
                                .MinimumLevel.Debug()
                                .MinimumLevel.Override("Microsoft.AspNetCore", LogEventLevel.Warning)
                                .Enrich.FromLogContext()
                                .CreateLogger();

            CreateHostBuilder(args).Build().Run();

            Log.CloseAndFlush();
        }

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

If you need to log the HTTP requests too. You have to configure the app service by adding the following line of code in Startup.cs.

app.UseSerilogRequestLogging();

And Then You can log the Error, Information or Fatal where you want as below.

using Microsoft.Extensions.Logging;

    [Route("api/[controller]")]
        [ApiController]
        public class TestController : ControllerBase
        {
            private readonly ILogger _logger;

            public TestController(ILogger<TestController> logger)
            {
                _logger = logger;
            }
            // GET api/values
            [HttpGet("{id}")]
            public ActionResult<IEnumerable<string>> Get(int id)
            {
                _logger.LogInformation("Start : Getting item details for {ID}", id);

                List<string> list = new List<string>();
                list.Add("A");
                list.Add("B");

                _logger.LogInformation("Completed : Item details for {ID}", list);
                return list;
            }
        }

If ASP.NET Core 3 MVC doesn't have such built-in functionality the code of using third-party logging providers will be acceptable for me.

MS officially recommends to use 3rd party file loggers.

Using Serilog is also very convenient in asp.net core 3.0:

1.program.cs

public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .UseSerilog((ctx, config) => { config.ReadFrom.Configuration(ctx.Configuration); })
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            });

2.appsettings.json

"Serilog": {
"Using": [ "Serilog.Sinks.Console", "Serilog.Sinks.File" ],

"WriteTo": [
  { "Name": "Console" },
  { "Name": "Debug" },
  {
    "Name": "File",
    "Args": {
      "path": "log-{Date}.txt",
      "rollingInterval": "Day",
      "shared": true
    }
  }
],
"Properties": {
  "Application": "SampleApp"
}
}

3.Use the following NuGet packages

<ItemGroup>    
    <PackageReference Include="Serilog.AspNetCore" Version="3.0.0" />
    <PackageReference Include="Serilog.Settings.Configuration" Version="3.1.1-dev-00209" />
    <PackageReference Include="Serilog.Sinks.File" Version="4.1.0" />  
</ItemGroup>

4. In controller:

public class HomeController : Controller
{
    private readonly ILogger<HomeController> _logger;

    public HomeController(ILogger<HomeController> logger)
    {
        _logger = logger;
    }

    public async Task Index()
    {
        _logger.LogInformation("Hello, World!");
    }
}

Then you could check the txt file existing in your project.

Refer to https://github.com/serilog/serilog-sinks-file