.Net Core EventLog - override unhandled exception are written to Application log

Question

I'have configured EventLog in my .Net Core 5.0 app to log application events to custom event log:

public Startup (IConfiguration configuration)
    {
        this.configuration = configuration;
        this.logger = LoggerFactory.Create(logging=>{
            logging.AddConsole();
            logging.AddEventLog(settings=> {
                settings.LogName = configuration["EventLogName"];
                settings.SourceName = configuration["EventLogSourceName"];
                settings.Filter = (category, level) =>  level >= LogLevel.Trace;
            });
        }).CreateLogger("Stage server logger");
    }

My logging configuration in appsettings:

    "Logging": {
    "LogLevel": {
        "Default": "Information",
        "Microsoft": "Warning",
        "Microsoft.Hosting.Lifetime": "Information"
    },
    "EventLog": {
        "LogLevel": {
            "Default": "Information"
        }
    }
}

Everything works just fine but some messages (especialy unhandled exceptions) are written to "Application" log instead of configuration["EventLogName"] log. Any idea how to configure the app to log all messages from the application to configuration["EventLogName"] log? Thanks a lot

Michal Rosenbaum · Accepted Answer · 2021-04-13T16:35:13.200

I see that you made an instance of the Logger in your startup.cs. I suppose you registered it in your DI? If yes, you don't see logs from all the sources because they are probably not using your Logger instance. You're simply configuring a specific Logger, not LoggerFactory.

Could you try something like this in the program.cs:

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureLogging((hostBuilder, logBuilder) => {
                logBuilder.AddConsole();
                logBuilder.AddEventLog(set => {
                    set.LogName = hostBuilder.Configuration["EventLogName"];
                    set.SourceName = hostBuilder.Configuration["EventLogSource"];
                    set.Filter = (category, level) => level >= LogLevel.Trace;
                });
            })
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            });

This way, I'm configuring Logger also for the code that I'm not controlling - dependencies.

But if you want a minimal effort solution to fix just unhandled exceptions, the quick fix would be creating a middleware with try-catch and rethrow with logging exception by your specific Logger injected by DI.

Michal thank you for your help, moving logging configuration to program.cs solved the problem. In DI I register LoggerFactory.Create(logging=>{ }).CreateLogger("Stage server logger"); and it's working exaclty as I need. Thanks! — kavanka, Apr 16 '21 at 11:33

.Net Core EventLog - override unhandled exception are written to Application log

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