Logging in C# Applications: Best Practices for Beginners

Introduction: Why is Logging Important?

Imagine your C# application is running in production. Suddenly, users report an error, but you can't figure out what went wrong. Without logs, you are like a pilot without instruments. Logging is the process of recording information about the application's operation: errors, warnings, debug messages, and key events.

In this article, we will cover the best logging practices for beginner C# (.NET) developers. You will learn how to set up logging, which tools to use, and how to avoid common mistakes.

1. Choosing a Logging Tool in C#

In the .NET ecosystem, there are several popular logging libraries. For beginners, we recommend three main options:

1.1. Built-in ILogger (Microsoft.Extensions.Logging)

Starting with .NET Core, Microsoft provides the built-in ILogger interface. It is simple to use and does not require installing third-party libraries.

using Microsoft.Extensions.Logging;\n\npublic class OrderService\n{\n    private readonly ILogger<OrderService> _logger;\n\n    public OrderService(ILogger<OrderService> logger)\n    {\n        _logger = logger;\n    }\n\n    public void ProcessOrder(int orderId)\n    {\n        _logger.LogInformation("Processing order {OrderId}", orderId);\n        // Processing logic\n    }\n}

1.2. Serilog — Flexible and Powerful

Serilog is one of the most popular libraries. It supports structured logging, making data analysis easy. Install via NuGet: Install-Package Serilog.AspNetCore

using Serilog;\n\npublic class Program\n{\n    public static void Main(string[] args)\n    {\n        Log.Logger = new LoggerConfiguration()\n            .MinimumLevel.Debug()\n            .WriteTo.Console()\n            .WriteTo.File("logs/app.log", rollingInterval: RollingInterval.Day)\n            .CreateLogger();\n\n        try\n        {\n            Log.Information("Application started");\n            CreateHostBuilder(args).Build().Run();\n        }\n        catch (Exception ex)\n        {\n            Log.Fatal(ex, "Application terminated with an error");\n        }\n        finally\n        {\n            Log.CloseAndFlush();\n        }\n    }\n}

1.3. NLog — Classic Choice

NLog is another mature library with extensive configuration options via configuration files.

// Configuration via appsettings.json\n{\n  "NLog": {\n    "targets": {\n      "console": {\n        "type": "Console",\n        "layout": "${longdate}|${level:uppercase=true}|${message}"\n      },\n      "file": {\n        "type": "File",\n        "fileName": "logs/app.log",\n        "layout": "${longdate}|${level:uppercase=true}|${message}"\n      }\n    },\n    "rules": [\n      { "logger": "*", "minLevel": "Info", "writeTo": "console,file" }\n    ]\n  }\n}

2. Log Levels: When to Use What

Proper use of log levels is the foundation of good practice. In C# (.NET), the following levels are defined (from most critical to least):

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• Trace (0) — extremely detailed debug information. Used only for deep diagnostics.
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• Debug (1) — debug messages for developers. Enabled in development environments but disabled in production.
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• Information (2) — general informational messages about application operation (startup, successful operations).
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• Warning (3) — warnings about potential issues that are not errors (e.g., exceeding execution time).
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• Error (4) — errors that require attention but are not fatal to the application.
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• Critical (5) — critical errors after which the app