31. C# (continue)

0. The Essence of continue

continue immediately stops the current iteration and moves to the next one.

Important distinction:

• ❌ It does not terminate the loop
• ⭕ It only skips the current cycle

Execution jumps directly to the next iteration.

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1. Simple Example — Skip Multiples of 3

Goal

Print numbers from 0 to 20, but exclude multiples of 3.

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Full Runnable Code

using System;

class Program
{
    static void Main()
    {
        for (int i = 0; i <= 20; i++)
        {
            if (i % 3 == 0)
            {
                continue;
            }

            Console.WriteLine(i);
        }

        Console.WriteLine("Loop finished.");
        Console.ReadKey();
    }
}

---

Execution Flow

Example when i = 6

6 % 3 == 0 → true
continue executes
Console.WriteLine(i) is skipped
loop proceeds to i++

So 6 is not printed.

The loop continues normally afterward.

---

Without continue

The same logic can be written like this:

if (i % 3 != 0)
{
    Console.WriteLine(i);
}

Both work.

However, the continue version follows a specific style:

Filter out exceptional cases first,
then let the normal logic run below.

This style is often called a guard clause approach.

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2. break vs continue

Keyword	Current iteration	Entire loop
break	Stops	Stops
continue	Stops	Continues

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break Example

for (int i = 0; i < 10; i++)
{
    if (i == 5)
    {
        break;
    }

    Console.WriteLine(i);
}

Output:

0
1
2
3
4

The loop stops completely.

---

continue Example

for (int i = 0; i < 10; i++)
{
    if (i == 5)
    {
        continue;
    }

    Console.WriteLine(i);
}

Output:

0
1
2
3
4
6
7
8
9

Only 5 is skipped.

---

3. Practical Scenario — Protecting User Input

Consider this code:

int number = int.Parse(input);

If the user enters:

abc

The program throws:

FormatException

and crashes.

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Goal

We want to:

• Ignore invalid input
• Ask again
• Prevent program crashes

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Safe Example Using continue

using System;

class Program
{
    static void Main()
    {
        string input;
        int userNumber = 0;

        do
        {
            Console.WriteLine("Enter number > 10 or type 'stop':");
            input = Console.ReadLine();

            if (input == "stop")
            {
                break;
            }

            bool isNumeric = true;

            foreach (char c in input)
            {
                if (!char.IsDigit(c))
                {
                    isNumeric = false;
                    break;
                }
            }

            if (!isNumeric)
            {
                Console.WriteLine("Invalid input.");
                continue;
            }

            userNumber = int.Parse(input);

        } while (userNumber <= 10);

        Console.WriteLine("Loop ended.");
        Console.ReadKey();
    }
}

---

Execution Flow Analysis

User enters "abc"

isNumeric = false
continue executes
int.Parse is skipped
loop starts next iteration

Result:

The program does not crash.

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4. Why break Did Not Cause an Initialization Error

Key idea:

break completely exits the loop.

Example:

if (input == "stop")
{
    break;
}

The code after this inside the loop is never executed.

So the compiler does not require all variables to be assigned.

---

But continue Is Different

continue jumps back to the loop condition.

Therefore:

All possible paths must still maintain valid variable states.

Otherwise the compiler will report errors.

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Structural Difference

From a control-flow perspective:

break

exit loop
continue execution outside

continue

skip current iteration
return to loop condition
start next iteration

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5. When continue Is Useful

Use continue when:

• many invalid conditions exist
• you want to filter early
• you want cleaner control flow

Typical pattern:

if (invalidCondition)
{
    continue;
}

// main logic below

This separates:

• exception cases
• normal execution

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Final Summary

break exits the entire loop.
continue skips only the current iteration and moves to the next one.