Username in Serilog file name in ASP.NET Core

Question

I have an ASP.NET Core Web API. I need to add the username to the Serilog file name. My appsettings.json file looks like this:

"Serilog": {
    "MinimumLevel": {
      "Default": "Information",
      "Override": {
        "Microsoft": "Warning",
        "Microsoft.Hosting.Lifetime": "Information"
      }
    },
    "WriteTo": [
      {       
        "Name": "File",
        "Args": {       
          "Path": "E:\\WebSite\\Development\\HealthAPI\\Logs\\log.txt",
          "rollingInterval": "Hour",
          "outputTemplate": "[{Timestamp:yyyy-MM-dd HH:mm:ss} {CorrelationId} {Level:u3}] [{Username}] {Message:lj}{NewLine}{Exception}"
        }
      }
    ]
  }

and this is program.cs:

var _logger = new LoggerConfiguration()
     .ReadFrom.Configuration(builder.Configuration)
     .MinimumLevel.Override("Microsoft.AspNetCore", LogEventLevel.Warning)
     .Enrich.FromLogContext()
     .CreateLogger();
builder.Logging.AddSerilog(_logger);

app.UseMiddleware<LogUserNameMiddleware>();
app.UseSerilogRequestLogging();

My middleware is

public class LogUserNameMiddleware
{
    private readonly RequestDelegate next;

    public LogUserNameMiddleware(RequestDelegate next)
    {
        this.next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        using (LogContext.PushProperty("UserName", context.User.Identity.Name ?? "anonymous"))
        {
            await next(context);
        }
    }
}

I need user name in the filename like Log_ABC_Date.txt.

Update 1 : I changed Program.cs :

  var _logger = new LoggerConfiguration()
 .WriteTo.Map("LoginController", "Other", (name, wt) => wt.File(@"E:\Logs\log-{name}.txt"))
 .MinimumLevel.Override("Microsoft.AspNetCore", LogEventLevel.Warning)
 .Enrich.FromLogContext()
 .CreateLogger();

And my controller :

 private readonly Serilog.ILogger _logger = Log.Logger.ForContext("LoginController","Username");

 _logger.Warning("Helllo !! {Name}",user.UserName);

Still this is giving issue. As Serilog.Sinks.Map is built around a mapping function, and as such, isn't able to be configured using JSON so I used Program.cs to configure Serilog.

Answer 1

According to Nicholas Blumhardt's suggestion, I implement it, please check below.

1. Project Structure

2. LogUserNameMiddleware.cs

using Serilog.Context;

namespace LogUserName1
{
    public class LogUserNameMiddleware
    {
        private readonly RequestDelegate _next;
        private readonly ILogger<LogUserNameMiddleware> _logger;

        public LogUserNameMiddleware(RequestDelegate next, ILogger<LogUserNameMiddleware> logger)
        {
            _next = next;
            _logger = logger;
        }

        public async Task Invoke(HttpContext context)
        {
            var userName = context.User.Identity.Name ?? "anonymous";
            using (LogContext.PushProperty("UserName", userName))
            {
                await _next(context);
            }
        }
    }

}

3. Program.cs

using Microsoft.AspNetCore.Authentication.Negotiate;
using Serilog.Events;
using Serilog;
using LogUserName1;

var builder = WebApplication.CreateBuilder(args);

var _logger = new LoggerConfiguration()
    .MinimumLevel.Override("Microsoft.AspNetCore", LogEventLevel.Information)
    .Enrich.FromLogContext()
    .WriteTo.Map(
        keyPropertyName: "UserName",
        defaultKey: "anonymous",
        (userName, logConfiguration) => logConfiguration.File($"E:\\WebSite\\Development\\HealthAPI\\Logs\\log_{userName}_{DateTime.Now:yyyy-MM-dd}.txt")
    )
    .CreateLogger();

builder.Logging.AddSerilog(_logger);

builder.Host.UseSerilog(_logger);

// Add services to the container.
builder.Services.AddControllersWithViews();

builder.Services.AddAuthentication(NegotiateDefaults.AuthenticationScheme)
   .AddNegotiate();

builder.Services.AddAuthorization(options =>
{
    // By default, all incoming requests will be authorized according to the default policy.
    options.FallbackPolicy = options.DefaultPolicy;
});
builder.Services.AddRazorPages();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Home/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();

app.UseAuthentication();
app.UseAuthorization();

app.UseMiddleware<LogUserNameMiddleware>();
app.UseSerilogRequestLogging();

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

app.Run();

4. Packages

5. Test Result