Table of Contents

• Introduction
• Implementation with MethodCallTarget
• Example
• References

Introduction

Generally, when using NLog to generate log messages within multiple class libraries or multiple classes, there are times when you need to process the message each time a log message occurs and display it on the GUI, or publish it to a Message Broker like GRPC, WebSocket, or Kafka.

Implementation with MethodCallTarget

In such cases, you can easily implement it using the MethodCallTarget class of NLog as shown below.

        // Define the callback function.
var target = new MethodCallTarget("LogNotify", async (logEvent, parameters) =>
{
    // Perform the desired processing here. If there are no asynchronous calls inside, remove the async above.
    if (logEvent.Level > NLog.LogLevel.Debug)
    {
    ...
    }
});

// Register the callback function to be called for all log message levels.
LogManager.Configuration.AddRuleForAllLevels(target);

// Update the logger configuration.
LogManager.ReconfigExistingLoggers();
        
    

Example

The example from the official website's documentation (https://nlog-project.org/documentation/v2.0.1/html/T_NLog_Targets_MethodCallTarget.htm) is as follows.

        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");
    }
}
        
    

References

For more information, please visit the NLog MethodCallTarget Documentation.