NLog: How do I control the format of a message from a LogEventInfo object?

Question

I'm new to NLog, and I've been playing with LogEventInfo objects, since I think I'll need them in my application. I created a LogEventInfo object with a plain text string, and then I called Logger.Debug(myEventInfoObject), using a FileAppender set up to write ${message}. Where I expected to see my text string, I saw instead the logger name, the message level, the message, and the sequence ID. I found that that expanded string is what I get when I call myEventInfoObject.ToString(). How can I control what appears when ${message} comes from a LogEventInfo object?

Here's my config file:

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      throwExceptions="true">
  <targets>
    <target name="file" xsi:type="File" layout="${longdate}  ${logger}  ${message}" fileName="${basedir}/nlog_sample_file.txt" />
  </targets>

  <rules>
    <logger name="*" minlevel="Debug" writeTo="file" />
  </rules>
</nlog>

Here's my code generating the log:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using NLog;

namespace NLogSample
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Logger logger = LogManager.GetCurrentClassLogger();
                LogEventInfo theEvent = new LogEventInfo(LogLevel.Debug, "", "This message from the LogInfoEvent will not be used.");
                theEvent.Properties["Message"] = "This message from the LogInfoEvent Message property will be used.";

                logger.Debug(theEvent);
                logger.Debug("Does the sequence ID show up in this message?");

                string formattedMessage = theEvent.FormattedMessage;
                string eventString = theEvent.ToString();
            }
            catch (Exception ex)
            {
                int a = 1;
            }
        }
    }
}

Finally, here is a sample of the message:

2014-10-08 10:14:13.5525 NLogSample.Program Log Event: Logger='' Level=Debug Message='This message from the LogInfoEvent will not be used.' SequenceID=2

I am working in Visual Studio 2012 on a Win7 Pro machine.

Thanks very much!

RobR

Answer 1

I had to do this

    class MyLogEventInfo : LogEventInfo {
        public override string ToString() {
            return base.FormattedMessage;
        }
    }

...

    var theEvent = new MyLogEventInfo();
    theEvent.Message = "This message from the LogInfoEvent will not be used.";
    logger.Debug(theEvent);

Answer 2

If you want to create LogEventInfo objects and fill them with your own information, you should use one of the Logger.Log method signatures, not the Logger.Info/Logger.Debug/etc method signatures.

The behavior you are seeing right now is probably because the Logger.Debug method is receiving an object (which happens to be a LogEventInfo object) and is calling ToString on it before logging it.

Answer 3

@wageoghe is right. Here is how I use it:

// Create the logger
Logger logger = LogManager.GetCurrentClassLogger();

// Create the LogEventInfo object
LogEventInfo logEvent = new LogEventInfo();

// Now add the event characteristics
logEvent.Properties["EventCode"] = eventId;
logEvent.Level = level;
logEvent.Message = message;
logEvent.Exception = ex;

// Actually write the log entry.
logger.Log(logEvent);

No need to use the wrapper log objects, just define your LogLevel using the Level property in LogEventInfo() and then pass that object to Log().