More Debugging Tactics

Vaibhav • September 11, 2025

In the previous article, we explored foundational debugging tactics like using Console.WriteLine, checking variable values, and isolating code. These are your first line of defense when something goes wrong. But as your programs grow-even with just int, string, and decimal-you’ll need a few more tools in your mental toolbox.

This article builds on what you already know and introduces deeper, more deliberate debugging techniques. These tactics are still simple, but they help you think more clearly, test more effectively, and fix bugs faster. No new C# features are introduced here-we’re still working within the boundaries of Chapter 1-but we’ll stretch your thinking and sharpen your instincts.

Use Echo Debugging to Confirm Flow and State

Echo debugging is the practice of printing out both the value and the context of a variable or operation. Instead of just printing a number, you print a message that explains what the number represents.

int quantity = 4;
decimal price = 12.5m;
decimal total = quantity * price;

Console.WriteLine("DEBUG: quantity = " + quantity);
Console.WriteLine("DEBUG: price = " + price);
Console.WriteLine("DEBUG: total = " + total);

This makes it easier to scan your output and understand what’s happening. If you see DEBUG: total = 50, you know exactly what that number means. It’s especially helpful when you’re printing multiple values in a row.

Validate Input Early and Clearly

Many bugs come from unexpected input. Even though we haven’t covered error handling yet, you can still write code that checks for obvious problems and prints helpful messages.

Console.WriteLine("Enter your age:");
string input = Console.ReadLine();

Console.WriteLine("DEBUG: raw input = " + input);

int age = int.Parse(input);
Console.WriteLine("Next year, you will be " + (age + 1));

If the user types something invalid, the program crashes. But by printing the raw input, you can at least see what caused the crash. Later, when you learn about error handling, you’ll be able to prevent the crash entirely. For now, this tactic helps you understand what went wrong.

Compare Intermediate Results

When a calculation goes wrong, don’t just look at the final result. Break the expression into parts and compare each one to what you expect.

int basePrice = 100;
int tax = 18;
int discount = 10;

int subtotal = basePrice + tax;
int finalPrice = subtotal - discount;

Console.WriteLine("Subtotal (base + tax): " + subtotal);
Console.WriteLine("Final price (subtotal - discount): " + finalPrice);

This lets you verify each step of the calculation. If the final price is wrong, you can check whether the subtotal was correct. This tactic is especially useful when you’re chaining multiple operations together.

Use Sentinel Values to Spot Uninitialized Variables

A sentinel value is a special value that you assign to a variable to indicate that it hasn’t been set yet. This helps you catch cases where a variable is used before it’s properly initialized.

int score = -1; // sentinel value

// ... later in the program
Console.WriteLine("Score: " + score);

If you see Score: -1 in your output, you know the variable was never updated. This is a simple but powerful tactic for catching logic errors.

Use Temporary Hardcoded Values to Isolate Bugs

If your program depends on user input or external data, try replacing it with hardcoded values temporarily. This helps you isolate the logic from the input.

// Original
Console.WriteLine("Enter quantity:");
string input = Console.ReadLine();
int quantity = int.Parse(input);

// Debug version
int quantity = 3; // hardcoded for testing

This lets you test the rest of your program without worrying about input errors. Once the logic is working, you can restore the original input code.

Repeat the Bug on Purpose

If your program behaves incorrectly only under certain conditions, try to recreate those conditions deliberately. This helps you understand what triggers the bug.

// Testing edge case
int apples = 0;
int oranges = 0;
int total = apples + oranges;

Console.WriteLine("Total fruits: " + total);

If the bug only happens when both values are zero, this test will reveal it. Once you can reproduce the bug consistently, you’re much closer to fixing it.

Use Output Markers to Track Execution

When your program has multiple sections, add markers to the output so you can see which parts are running.

Console.WriteLine("=== Start of Program ===");

int a = 5;
int b = 10;
Console.WriteLine("DEBUG: a = " + a + ", b = " + b);

Console.WriteLine("=== End of Program ===");

These markers help you confirm that the program is running from top to bottom, and they make it easier to spot where things go wrong.

Use Visual Alignment to Spot Mistakes

Sometimes, bugs hide in plain sight because the code isn’t visually aligned. Use consistent indentation and spacing to make your code easier to read-and easier to debug.

// Hard to read
int a=5;int b=10;int c=a+b;Console.WriteLine(c);

// Easier to read
int a = 5;
int b = 10;
int c = a + b;
Console.WriteLine(c);

Clean code isn’t just about style-it’s about clarity. And clarity is your best friend when debugging.

Use Comments to Explain What Should Happen

When you’re debugging, write comments that describe what each line is supposed to do. This helps you compare your intent with the actual behavior.

// Calculate total cost
int quantity = 2;
decimal price = 15.0m;
decimal total = quantity + price; // should be quantity * price

Console.WriteLine("Total: " + total);

The comment reveals the mistake. You meant to multiply, but you added instead. Writing down your intent helps you spot mismatches between what you meant and what you wrote.

Keep a Debugging Checklist

When you’re stuck, run through a mental checklist:

• Did I print the variable values?
• Did I check the input?
• Did I break down the calculation?
• Did I test with hardcoded values?
• Did I isolate the problem?

This checklist helps you stay focused and avoid random guessing. Debugging is a process, not a guessing game.

Summary

In this article, we explored more advanced-but still beginner-friendly-debugging tactics. These techniques help you think more clearly, test more effectively, and fix bugs faster:

• Echo debugging with context-rich print statements
• Validating input and using sentinel values
• Breaking down calculations and comparing intermediate results
• Hardcoding values to isolate logic
• Using output markers and visual alignment for clarity
• Writing comments to express intent
• Following a debugging checklist to stay focused

These tactics are simple, but they’re powerful. They help you build confidence, reduce frustration, and develop the habits of a thoughtful, methodical programmer. In the next article, we’ll explore how to use an integrated debugger-stepping through code, setting breakpoints, and watching variables in real time.