C# Checked & Unchecked Example: Handle Overflow Easily

Ever faced weird number issues in C#? You add two big numbers, and boom! Instead of a massive sum, you get a strange negative number. That’s called integer overflow, and it can mess up your calculations.

Now, C# provides two cool tools to deal with this— checked and unchecked statements. They help control how C# handles overflow errors. Sounds interesting? Let’s dive in!

What You Are Going to Learn in This Lesson?

✅What checked and unchecked statements are
✅Why they are useful in C#
✅A real-world example to understand better
✅Hands-on coding with step-by-step explanation.

1. Checked Statement

Alright, let’s keep it simple! Imagine you’re carrying a glass full of water. If you keep pouring more water into it, at some point, it overflows and makes a mess. Now, what if you had a magical cup that warns you before it spills? That’s exactly what a checked statement does in C#!

When you’re working with numbers in programming, sometimes they get too big and overflow—like when a water glass can’t hold more liquid. If you don’t check for overflow, the number might turn into something completely unexpected (like negative when it should be positive). That’s a disaster, right?

This is where the checked statement comes to the rescue! It monitors your numbers and if an overflow happens, it stops the program and throws an error. That way, you know something went wrong instead of letting weird numbers ruin your calculations.

Why Use a Checked Statement?

Here are some real-world reasons why you should use it:

✅ Prevents unexpected results – Without checking, a number can flip to something completely wrong.
✅ Catches mistakes early – Instead of hunting down weird bugs later, your program stops immediately when an overflow happens.
✅ Great for important calculations – If you’re dealing with money, scores, or anything critical, you don’t want errors slipping through.
✅ Makes debugging easier – You’ll immediately know where the problem is, rather than scratching your head over mysterious numbers.

When Should You Use It?

👉 When working with large numbers – If your numbers grow big fast, better be safe than sorry.
👉 When precision matters – Financial apps, game scores, or scientific calculations should always be checked.
👉 When you want safer code – It helps you avoid sneaky bugs that can break your program later.

In short, a checked statement is like a safety net—it protects your program from number overflow disasters! 🚀

Checked Example (Throws Error on Overflow)

				
					using System;

class Program
{
    static void Main()
    {
        try
        {
            checked
            {
                int num = int.MaxValue;
                num += 1; // Overflow happens here
            }
        }
        catch (OverflowException ex)
        {
            Console.WriteLine("Oops! Overflow detected: " + ex.Message);
        }
    }
}

Output

				
					Oops! Overflow detected: Arithmetic operation resulted in an overflow.

Explanation:

checked ensures that overflow throws an exception.
int.MaxValue is the highest value an int can store.
Adding 1 to it causes an overflow.
The program catches the error and displays a friendly message.

2. Unchecked Statement

Alright, imagine you’re filling a water glass again. But this time, instead of stopping when it overflows, you just keep pouring—and whatever spills, spills. No warnings, no stopping, just let it happen. That’s exactly what an unchecked statement does in C#!

When numbers get too big in programming, they overflow. Without any checks, the program just keeps running, even if the number turns into something completely unexpected. Instead of throwing an error, it silently ignores the problem, which might lead to weird results later.

Why Use an Unchecked Statement?

There are a few reasons why you might let things slide instead of stopping the program:

✅ Faster execution – Without checking for overflow, your program runs slightly quicker.
✅ You know what you’re doing – If you’re handling values that are safe, checking might be unnecessary.
✅ You don’t care about overflow – Sometimes, you just want to let numbers wrap around and move on.

When Should You Use It?

👉 When performance matters – If you’re doing a lot of number crunching and need speed, unchecked might help.
👉 When overflow isn’t a big deal – If the result doesn’t break your logic, you can ignore it.
👉 When you’re working with non-critical data – For example, in small calculations where a wrong value won’t cause a disaster.

But be careful! An unchecked statement is like driving without seat belts—it might be fine most of the time, but when things go wrong, they go really wrong. So, use it wisely! 😃

Unchecked Example (Ignores Overflow)

				
					using System;

class Program
{
    static void Main()
    {
        unchecked
        {
            int num = int.MaxValue;
            num += 1; // Overflow happens, but no error!
            Console.WriteLine("New Value: " + num);
        }
    }
}

Output

				
					New Value: -2147483648

Explanation:

unchecked ignores overflow. No exception is thrown.
Instead of crashing, the number wraps around to a negative value.
This can lead to unexpected bugs if not handled properly.

3. Real-World Example: Bank Account Balance Overflow

Imagine a banking system where transactions are stored in an int. If unchecked, a big deposit could break the system!

Checked for Safety

				
					using System;

class BankAccount
{
    public int Balance { get; private set; } = 1000000000; // 1 Billion

    public void Deposit(int amount)
    {
        try
        {
            checked
            {
                Balance += amount; // Prevent overflow
            }
        }
        catch (OverflowException)
        {
            Console.WriteLine("Oops! Transaction too big. Contact support.");
        }
    }
}

class Program
{
    static void Main()
    {
        BankAccount account = new BankAccount();
        account.Deposit(int.MaxValue); // Huge deposit causing overflow
        Console.WriteLine("Final Balance: " + account.Balance);
    }
}

Output

				
					Oops! Transaction too big. Contact support.
Final Balance: 1000000000

What Happened?

Checked prevents the balance from becoming a nonsense number.
Instead of corrupting data, an error message appears.
Without checked, the balance could have gone negative!

When to Use Checked and Unchecked?

Scenario	Use Checked?	Use Unchecked?
You want to catch errors early ✅	✅ Yes	❌ No
You need maximum speed and don’t care about overflow	❌ No	✅ Yes
Dealing with critical data like money	✅ Yes	❌ No
Small calculations with known values	❌ No	✅ Yes

Conclusion

Now you know how to handle overflow like a pro! 🎉

checked keeps your program safe by throwing errors.
unchecked lets things run faster but can lead to weird results.
Always use checked when working with important data like money or scores.

Try out the examples and see how they work in different situations! If you have difficulty or a question, drop a comment. We will be happy to help you. 😊

Next What?

In the next lesson, you’ll learn about the Lock Statement—super useful for handling multiple threads safely. Stay tuned! 🚀

Complete C# Tutorial

C# Checked & Unchecked Example: Handle Overflow Easily

What You Are Going to Learn in This Lesson?

1. Checked Statement

Why Use a Checked Statement?

When Should You Use It?

Checked Example (Throws Error on Overflow)

Explanation:

2. Unchecked Statement

Why Use an Unchecked Statement?

When Should You Use It?

Unchecked Example (Ignores Overflow)

Explanation:

3. Real-World Example: Bank Account Balance Overflow

Checked for Safety

What Happened?

When to Use Checked and Unchecked?

Conclusion

Next What?

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