12. Debugging and Logging

Let’s go through debugging and logging in C# — essential tools for finding and fixing issues and monitoring application behavior.

---

📌 1. Debugging in C#

Debugging is the process of examining your code while it runs to identify and fix errors.

Common Techniques

1. Breakpoints

   • Set in Visual Studio or VS Code to pause execution at a specific line.

   • Allows you to inspect variables, watch expressions, and step through code.

2. Step Execution

   • Step Into (F11) → enter a method call

   • Step Over (F10) → execute the method without entering it

   • Step Out (Shift+F11) → exit current method

3. Watch & Immediate Window

   • Monitor variables and evaluate expressions during debugging.

4. Conditional Breakpoints

   • Break only when a condition is true:

     // Example: break when i == 5
     if(i == 5) { /* breakpoint here */ }

---

📌 2. Logging in C#

Logging is recording information about your application’s execution to help debug, monitor, or audit behavior.

Using Console.WriteLine (Simple Logging)

int x = 5;
Console.WriteLine($"Value of x: {x}");

• Quick and easy for small apps or testing, but not ideal for production

---

Using System.Diagnostics.Debug

using System.Diagnostics;
 
Debug.WriteLine("This is a debug message");
Debug.WriteLine($"Variable value: {x}");

• Outputs messages to Output window in Visual Studio

• Only visible in Debug builds, not Release

---

Using ILogger and Logging Frameworks

• ASP.NET Core provides built-in logging via ILogger

• Supports multiple targets: console, files, databases, etc.

using Microsoft.Extensions.Logging;
 
public class Program
{
    private readonly ILogger<Program> _logger;
 
    public Program(ILogger<Program> logger)
    {
        _logger = logger;
    }
 
    public void Run()
    {
        _logger.LogInformation("Application started");
        _logger.LogWarning("This is a warning");
        _logger.LogError("An error occurred");
    }
}

---

Popular Logging Libraries

Library	Description
NLog	Flexible, multiple targets
Serilog	Structured logging, JSON output
log4net	Classic logging framework

• These libraries allow file logging, rolling logs, and structured logging

---

📌 3. Best Practices

1. Use proper log levels: Debug, Info, Warning, Error, Critical

2. Avoid excessive logging in performance-critical code

3. Include context: timestamps, user ID, method names

4. Separate Debug and Production logging

5. Dispose or close loggers properly if writing to files

---

📌 4. Summary Table

Feature	Description
Breakpoints	Pause execution to inspect code
Step Execution	Navigate through code line by line
Debug.WriteLine	Quick debug messages in development
Console.WriteLine	Simple logging to console
ILogger / NLog / Serilog	Structured, production-ready logging
Best Practices	Proper log levels, context, avoid performance hits

---

✅ Tip:

• Combine debugging for immediate problem solving and logging for long-term monitoring.

• Structured logging (with Serilog or NLog) is preferred for production apps.