To set up the target in the configuration file, use the following syntax:

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> 
  <targets> 
    <target name="m" xsi:type="MethodCall" className="Example, MethodCall" 
            methodName="LogMethod"> 
      <parameter layout="${level}"/> 
      <parameter layout="${message}"/> 
    </target> 
  </targets> 
  <rules> 
    <logger name="*" minlevel="Debug" writeTo="msgbox"/> 
  </rules> 
</nlog> 

This assumes just one target and a single rule. More configuration options are described here.

To set up the log target programmatically use code like this:

using System; 
 
using NLog; 
using NLog.Targets; 
using System.Diagnostics; 
 
public class Example 
{ 
    public static void LogMethod(string level, string message) 
    { 
        Console.WriteLine("l: {0} m: {1}", level, message); 
    } 
    static void Main(string[] args) 
    { 
        MethodCallTarget target = new MethodCallTarget(); 
        target.ClassName = typeof(Example).AssemblyQualifiedName; 
        target.MethodName = "LogMethod"; 
        target.Parameters.Add(new MethodCallParameter("${level}")); 
        target.Parameters.Add(new MethodCallParameter("${message}")); 
 
        NLog.Config.SimpleConfigurator.ConfigureForTargetLogging(target, LogLevel.Debug); 
 
        Logger logger = LogManager.GetLogger("Example"); 
        logger.Debug("log message"); 
        logger.Error("error message"); 
    } 
}