Dynamically set EventID when logging to Event Viewer using Serilog

Question

Currently, I have set up my logger to log to the event viewer like so:

 Log.Logger = new LoggerConfiguration()
               .MinimumLevel.Information()
               .MinimumLevel.Override("Microsoft", LogEventLevel.Warning)
               .Enrich.FromLogContext()
               .WriteTo.EventLog("MySource", "EventViewerArea")
               .CreateLogger();

When I log I use the following command:

_logger.LogWarning(logText);

It looks as though I can pass in the EventId to the LogWarning method, so I wanted to set it when running the LogWarning/LogInformation methods:

_logger.LogWarning(9876, logText);

But this does not override the Event ID in the entry in the Event Viewer. Any ideas on how I can dynamically set this EventId when logging? I need to have this dynamic and not set to one value when instantiating the logger.

Thanks in advance

Answer 1

I was able to solve this with the following steps:

Add the following when instantiating the logger:

.WriteTo.EventLog("SourceInEventViewer", 
    "AreaInEventViewer", 
    formatProvider: new EventLogFormatProvider(),
    eventIdProvider: new EventIdProvider(),
    manageEventSource: true,
    restrictedToMinimumLevel: LogEventLevel.Information)

Add the following class to the project

using Newtonsoft.Json.Linq;
using Serilog.Events;
using Serilog.Sinks.EventLog;
using System;
using System.Linq;

namespace IndependentFile.Extensions
{
    public class LoggerSetupExtensions
    {
        public class EventLogFormatProvider : IFormatProvider, ICustomFormatter
        {
            public object GetFormat(Type formatType)
            {
                return formatType == typeof(ICustomFormatter) ? this : null;
            }

            public string Format(string format, object arg, IFormatProvider formatProvider)
            {
                return arg.ToString();
            }
        }       

        public class EventIdProvider : IEventIdProvider
        {
            public ushort ComputeEventId(LogEvent logEvent)
            {
                var eventTypeProp = logEvent.Properties.FirstOrDefault(prop => prop.Key == "EventId");

                if (eventTypeProp.Value == null)
                {
                    return (ushort)LogValuesEnum.Unknown;
                }
                try
                {
                    var val = eventTypeProp.Value;
                    string eventType = eventTypeProp.Value.ToString();

                    //this is not the right way to parse the logEventPropertyValue
                    var parseEventType = JObject.Parse(eventType);

                    var eventIdInt = parseEventType["Id"].ToString();

                    if (eventType == null) return (int)LogValuesEnum.Unknown;

                    var tryParseEventId = Enum.TryParse<LogValuesEnum>(eventIdInt, ignoreCase: true, out var res);
                    if (tryParseEventId)
                    {
                        return (ushort)res;
                    }

                    return (ushort)LogValuesEnum.Unknown;
                }
                catch(Exception exc)
                {
                    return (ushort)LogValuesEnum.Unknown;
                }

            }
        }
    }
}

Now you can use the log and pass your event id to that:

_logger.LogInformation(LogValuesEnum.MyEnumVal, "My log message");