How to write logs to EventLog by ILogger<T> in ASP.NET Core?

Question

I follow this document Logging in .NET Core and ASP.NET Core, try to write log to Windows EventLog.

first, I create Source and Log in Windows Event Log:

if (!EventLog.SourceExists("MyTestSource"))
{
    EventLog.CreateEventSource("MyTestSource", "MyTestLog");
    return;
}

and it's created.

then, I configured logging in CreateHostBuilder from Program.cs of my ASP.NET Core app (core 3.0):

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureLogging(logging =>
        {
            logging.ClearProviders();
            logging.AddEventLog(new EventLogSettings
            {
                SourceName = "MyTestSource",
                LogName = "MyTestLog"
            });
        })
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseStartup<Startup>();
        });

I think that's all. Then I use logger in my controller:

[Route("[controller]")]
[ApiController]
public class ServerController : ControllerBase
{
    ILogger<ServerController> _logger = null;
    public ServerController(ILogger<ServerController> logger)
    {
        _logger = logger;
    }

    [HttpGet("GetServerInfo")]
    public string GetServerInfo()
    {
        _logger.LogInformation("GetServerInfo Called");
        return "Hello I'm Server";
    }
}

but there's nothing in MyTestLog in Windows EventLog. Is there anything I missed?

pfx · Accepted Answer · 2020-12-21 20:24:50Z

You can go for a configuration only approach, leaving your existing CreateHostBuilder code as-is.

As mentioned in the document you linked, under the Windows Eventlog section, the EventLogProvider defaults to the warning level when not explicitly configured:

Unlike the other providers, the EventLog provider does not inherit the default non-provider settings.
If EventLog log settings aren't specified, they default to LogLevel.Warning.

To lower this logging level to Information, you have to foresee an explicit entry for the EventLog provider in the Logging section of your appsettings.{Environment}.json file.

E.g.: appsettings.Development.json:

{
    "Logging": {
        "LogLevel": {
            "Default": "Debug",
            "System": "Information",
            "Microsoft": "Information"
        },
        "EventLog": {
            "LogLevel": {
                "Default": "Information"
            }
        }
    }
}

Gio Tabidze · Accepted Answer · 2020-02-24 14:49:38Z

6

+200

It's caused by Host.CreateDefaultBuilder(args), which executes:

.ConfigureLogging(loggingBuilder => {
    loggingBuilder.AddFilter<EventLogLoggerProvider>((Func<LogLevel, bool>) (level=>level>=LogLevel.Warning));
}

under the hood. Warning is 1 level higher than Information, so...

As a solution, you can create fresh HostBuilder using new HostBuilder() and configure it from scratch or override that behavior by calling .ConfigureLogging after creating default host builder.

edited Feb 24, 2020 at 14:49

answered Feb 24, 2020 at 14:41

Gio Tabidze

3612 silver badges4 bronze badges

Comments

Paul Lorica · Accepted Answer · 2019-12-04 21:01:05Z

2

Try bumping up your logging to _logger.LogError("GetServerInfo Called"") and see if it works. If it does, then you will have to set up your log filtering

answered Dec 4, 2019 at 21:01

Paul Lorica

7735 silver badges6 bronze badges

1 Comment

David Tsui Over a year ago

hi Paul, LogError can write into Windows EventLog, but LogInformation not work, how to make it work?

Collectives™ on Stack Overflow

How to write logs to EventLog by ILogger<T> in ASP.NET Core?

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related