ASP.NET Core logging in 2 different files

Question

When using the default ASP.NET core logging in combination with Serilog, is it possible to write errors to errors.log and information to informations.log

using Microsoft.Extensions.Logging;
using Serilog;

loggerFactory.AddSerilog();
loggerFactory.AddFile(Configuration.GetSection("Logging"));

Appsettings.json:

"Logging": {
    "PathFormat": "path-{Date}.log",
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Information",
      "System": "Information",
      "Microsoft": "Information"
    }
  }

I want one logging file where I can see the requests which are done and stuff like that, just the info log. And one log with errors for debugging purposes. How can I log different things to 2 files?

Answer 1

If you want to use a single Logger object you can filter log type by level:

using Serilog;
using Serilog.Events;

Log.Logger = new LoggerConfiguration()
            // Restricts logs to: Debug, Information, Warning, Error and Fatal
            .MinimumLevel.Debug()
            // Logs Information, Warning, Error and Fatal to "info-logs.txt" file
            .WriteTo.File(path: "info-logs.txt", restrictedToMinimumLevel: LogEventLevel.Information)
            // Logs Error and Fatal to "error-logs.txt" file
            .WriteTo.File(path: "error-logs.txt", restrictedToMinimumLevel: LogEventLevel.Error) 
            .CreateLogger();

Log.Verbose("Loggin Verbose..."); // Won't log, because the Logger "MinimumLevel" is set to Debug
Log.Debug("Loggin Debug..."); // Won't log, because there is no sink that takes Debug
Log.Information("Loggin Information..."); // Logs into "info-logs.txt"
Log.Warning("Loggin Warning..."); // Logs into "info-logs.txt"
Log.Error("Loggin Error..."); // Logs into "info-logs.txt" and "error-logs.txt"
Log.Fatal("Loggin fatal..."); // Logs into "info-logs.txt" and "error-logs.txt"

The log levels and descriptions from the docs :

Answer 2

Serilog supports that but you seem to be missing relevant code. In your Startup method you should be setting up your SeriLog configuration. There you can configure it to log different data into different files using sinks and filters.