Basic Debugging Tactics

Vaibhav • September 11, 2025

Now that you understand what debugging is and why it matters, it’s time to get tactical. In this article, we’ll explore practical, beginner-friendly techniques you can use to find and fix bugs in your C# programs. These tactics don’t require any advanced tools or programming concepts-just a sharp eye, a curious mind, and the foundational knowledge you’ve already built in Chapter 1.

We’ll focus on simple, repeatable actions you can take when your program doesn’t behave as expected. These tactics are especially useful when working with basic types like int, string, and decimal, and when your code is still small and manageable.

Use Console.WriteLine as a Debugging Lens

The most accessible and powerful debugging tool at this stage is Console.WriteLine. It lets you peek inside your program while it’s running. You can print out variable values, track the flow of execution, and verify assumptions-all without needing any special software.

int quantity = 2;
decimal price = 9.99m;
decimal total = quantity + price;

Console.WriteLine("Quantity: " + quantity);
Console.WriteLine("Price: " + price);
Console.WriteLine("Total: " + total);

This code prints:

Quantity: 2
Price: 9.99
Total: 11.99

That’s a red flag. You meant to multiply, not add. By printing the values, you caught the mistake immediately. This is the essence of tactical debugging: observe, compare, correct.

Print Before You Crash

If your program crashes, try printing values just before the line that fails. This helps you understand what led to the crash.

Console.WriteLine("Enter a number:");
string input = Console.ReadLine();
int number = int.Parse(input);
Console.WriteLine("You entered: " + number);

If the user types ten, the program crashes. To debug this, add a print statement before the parsing:

Console.WriteLine("Raw input: " + input);

Now you can see exactly what the user typed. This helps you understand why the parsing failed.

Check Your Variable Values Often

Bugs often come from variables holding unexpected values. Maybe you assigned the wrong value, or maybe the value changed in a way you didn’t expect. Either way, printing the variable helps.

int apples = 5;
int oranges = 3;
int total = apples + apples;

Console.WriteLine("Apples: " + apples);
Console.WriteLine("Oranges: " + oranges);
Console.WriteLine("Total: " + total);

The output shows:

Apples: 5
Oranges: 3
Total: 10

That’s wrong. You meant to add apples and oranges. The print statements helped you catch the typo.

Trace the Flow of Execution

Sometimes the problem isn’t with the values-it’s with the order in which things happen. You can use print statements to trace the flow of your program.

Console.WriteLine("Start");
Console.WriteLine("Step 1");
Console.WriteLine("Step 2");
Console.WriteLine("End");

If one of these lines doesn’t appear in the output, you know the program didn’t reach that point. That tells you where to look.

Use Temporary Variables to Simplify Expressions

If a calculation isn’t working, break it into smaller steps. Assign each part to a temporary variable and print it. This makes it easier to spot where things go wrong.

int a = 10;
int b = 5;
int c = 2;

int result = a + b * c;
Console.WriteLine("Result: " + result);

This prints Result: 20, which might surprise you. To debug it, break it down:

int product = b * c;
int result = a + product;

Console.WriteLine("Product: " + product);
Console.WriteLine("Result: " + result);

Now it’s clear: multiplication happens before addition. This helps you understand operator precedence and fix the logic if needed.

Compare Expected vs Actual Output

Before you run your program, write down what you expect it to print. Then run it and compare. If the output doesn’t match, you know there’s a bug.

int x = 4;
int y = 6;
int average = x + y / 2;

Console.WriteLine("Average: " + average);

You might expect 5, but the output is 7. That’s because y / 2 is 3, and x + 3 is 7. The fix is to use parentheses:

int average = (x + y) / 2;

Now the output is correct.

Comment Out Code to Narrow the Problem

If your program is large, comment out parts of it to isolate the bug. This helps you focus on the section that’s causing trouble.

// Console.WriteLine("Step 1");
// Console.WriteLine("Step 2");
Console.WriteLine("Step 3");

If the bug disappears when you comment out a line, that line is probably the culprit.

Use Meaningful Variable Names

Debugging is easier when your variables have clear, descriptive names. If you see int x = 5;, you don’t know what x represents. But if you see int itemCount = 5;, it’s much clearer.

This helps you reason about your code and spot mistakes more easily.

Keep Your Code Neat and Aligned

Bugs love messy code. If your indentation is inconsistent or your lines are too long, it’s harder to see what’s going on. Keep your code clean and aligned. Use blank lines to separate sections. Use consistent spacing.

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

Don’t Assume-Verify

It’s easy to assume that a variable has the right value or that a line of code is working. But assumptions are dangerous. Always verify.

If you think total should be 100, print it. If you think a line of code is being executed, add a print statement to confirm.

Debugging is about replacing assumptions with evidence.

Practice Makes You Faster

The more you debug, the better you get. You’ll start to recognize common patterns. You’ll learn to spot typos, logic errors, and off-by-one mistakes quickly. You’ll develop an instinct for where bugs like to hide.

But that only comes with practice. So don’t be discouraged when you hit a bug. Treat it as a puzzle. Use your tactics. And enjoy the process.

Summary

In this article, we explored a set of basic debugging tactics that you can use right now, with the tools and knowledge you already have:

• Use Console.WriteLine to inspect variables and trace execution
• Print values before a crash to understand what went wrong
• Break down complex expressions into smaller parts
• Compare expected vs actual output to spot logic errors
• Comment out code to isolate the problem
• Use clear variable names and neat formatting to reduce confusion
• Verify your assumptions with evidence

These tactics may seem simple, but they’re powerful. They form the foundation of every professional developer’s debugging toolkit. As your programs grow more complex, you’ll build on these techniques with more advanced tools. But for now, these are more than enough to help you find and fix most beginner-level bugs.

In the next article, we’ll go beyond the basics and explore more debugging tactics-techniques that help you dig deeper, think more clearly, and solve tougher problems with confidence.