How to retain callsite information when wrapping NLog

internal string GetCallingMethodName()
{
  string result = "unknown";
  StackTrace trace = new StackTrace(false);
  for (int i = 0; i < trace.FrameCount; i++)
  {
    StackFrame frame = trace.GetFrame(i);
    MethodBase method = frame.GetMethod();
    Type dt = method.DeclaringType;
    if (!typeof(ILogger).IsAssignableFrom(dt) && method.DeclaringType.Namespace != "DiagnosticsLibrary")
    {
      result = string.Concat(method.DeclaringType.FullName, ".", method.Name);
      break;
    }
  }
  return result;
}

Source : http://slf.codeplex.com/discussions/210075

I used the posted code above to simply extract the calling method name and pass that as part of the "message" parameter to the layout. This lets me have the original method name where the log wrapper was called be written to the log file (rather than the log wrapper's class name).

To skip few frames and dive into wrapper callers context, set up in the App.config, or in program the famous modifier:

skipFrames=1

Examples: See this page for ${callsite:skipFrames=Integer} and this page for ${callsite-linenumber:skipFrames=Integer}

I recommend you to use this format in your wrapper:

${callsite:fileName=true:includeSourcePath=false:skipFrames=1}

The output from this setting will be as follows:

... {LicenseServer.LSCore.MainThreadFunction(LSCore.cs:220)} ...

The problem is that your wrapper is not wrapping correctly. Here is an example of how to wrap NLog correctly, taken directly from the source tree of NLog:

using System;
using System.Text;
using NLog;

namespace LoggerWrapper
{    
  /// <summary>    
  /// Provides methods to write messages with event IDs - useful for the Event Log target.    
  /// Wraps a Logger instance.    
  /// </summary>    
  class MyLogger    
  {        
    private Logger _logger;        

    public MyLogger(string name)        
    {            
      _logger = LogManager.GetLogger(name);        
    }        

    public void WriteMessage(string eventID, string message)           
    {            
      ///            
      /// create log event from the passed message            
      ///             
      LogEventInfo logEvent = new LogEventInfo(LogLevel.Info, _logger.Name, message);


      //
      // set event-specific context parameter            
      // this context parameter can be retrieved using ${event-context:EventID}            
      //            
      logEvent.Context["EventID"] = eventID;            
      //             
      // Call the Log() method. It is important to pass typeof(MyLogger) as the            
      // first parameter. If you don't, ${callsite} and other callstack-related             
      // layout renderers will not work properly.            
      //            
      _logger.Log(typeof(MyLogger), logEvent);        
    }    
  }
}

The key is passing the type of your logger wrapper to the call to Log. When NLog tries to find the callsite, it goes up the stack until the first calling method whose declaring type is NOT the type passed to the Log call. This will be the code that is actually calling your wrapper.

In your case, your logger would look something like this:

    public void Log(LogType messageType, Type context, string message, Exception exception)
    {
        NLog.Logger logger = NLog.LogManager.GetLogger(context.Name);
        LogLevel logLevel = LogLevel.Info; // Default level to info

        switch (messageType)
        {
            case LogType.Debug:
                logLevel = LogLevel.Debug;
                break;
            case LogType.Info:
                logLevel = LogLevel.Info;
                break;
            case LogType.Warning:
                logLevel = LogLevel.Warn;
                break;
            case LogType.Error:
                logLevel = LogLevel.Error;
                break;
            case LogType.Fatal:
                logLevel = LogLevel.Fatal;
                break;
            default:
                throw new ArgumentException("Log message type is not supported");                    
        }

        //
        // Build LogEvent here...
        //
        LogEventInfo logEvent = new LogEventInfo(logLevel, context.Name, message);
        logEvent.Exception = exception;

        //
        // Pass the type of your wrapper class here...
        //
        logger.Log(typeof(YourWrapperClass), logEvent);
    }