Logging in C# (.NET): Overview of Best Solutions and Libraries

Logging in C# (.NET): Overview of Best Solutions and Libraries

Logging is not just about writing messages to a file. In modern C# (.NET) development, it is a powerful tool for monitoring, debugging, and analyzing application behavior. Properly configured logging allows you to quickly find errors, track performance, and build analytics. In this article, we will review the most popular and effective libraries for .NET, as well as best practices for using them.

Why is professional logging needed?

Basic Console.WriteLine or Debug.Write are not suitable for a production environment. Real logging frameworks provide:

• Log Levels (Trace, Debug, Information, Warning, Error, Critical) — filtering message importance.
• Structured Data — logs in JSON format that are easy to parse (ELK, Splunk).
• Multiple Sinks/Targets — writing to file, console, database, cloud services (Azure, AWS).
• Configuration — adjusting behavior without recompiling code.
• Asynchrony — minimizing impact on application performance.

Top Libraries for .NET

Let's look at four main solutions that dominate the .NET ecosystem.

1. Serilog — The Standard for Structured Logging

Serilog is the most popular library for .NET, which first popularized the concept of structured logging. Instead of concatenating strings, you pass a template and parameters, allowing data to be saved in a machine-readable format.

Key Features:

• Deep integration with .NET Core / .NET 5+.
• Huge number of Sinks (Serilog.Sinks.Console, Serilog.Sinks.File, Serilog.Sinks.ElasticSearch).
• Support for Enrichers to automatically add context (machine name, application version, ThreadId).
• Clean and concise API.

Example of configuring and using Serilog:

using Serilog;

// Configuration in Program.cs (.NET 6+)Log.Logger = new LoggerConfiguration()    .MinimumLevel.Information()    .WriteTo.Console()    .WriteTo.File("logs/app-.log", rollingInterval: RollingInterval.Day)    .Enrich.WithMachineName()    .CreateLogger();

try{    Log.Information("Application started");    var userId = 123;    Log.Information("User {UserId} logged in", userId);    // Example with exception    throw new InvalidOperationException("Test error");}catch (Exception ex){    Log.Error(ex, "A critical error occurred in method {Method}", nameof(Main));}finally{    Log.CloseAndFlush();}

2. NLog — Flexible and Performant

NLog is one of the oldest frameworks that handles high-load systems excellently. Its main feature is flexible rule routing and built-in support for asynchronous writing "out of the box".

Key Features:

• Support for XML, JSON, and code-based configuration.
• Built-in support for log rotation by size and time.
• Extensibility through custom Targets.
• Lower memory consumption compared to Serilog in some scenarios.

Example of configuring NLog via code:

using NLog;using NLog.Config;using NLog.Targets;

// Logger configurationvar config = new LoggingConfiguration();var consoleTarget = new ConsoleTarget("console");config.AddRule(LogLevel.Info, LogLevel.Fatal, consoleTarget);

var fileTarget = new FileTarget("file"){    FileName = "${basedir}/logs/${shortdate}.log",    Layout = "${longdate} | ${level:uppercase=true} | ${message} ${exception:fo