C# - Continue

C# - The continue Statement

Introduction to the continue Statement

The continue statement in C# provides a way to immediately stop the current iteration of a loop and proceed to the next one. Unlike the break statement, which terminates the entire loop, continue only skips the remaining code within the current iteration.

Its behavior depends on the type of loop:

• In a for loop, it jumps to the loop’s increment expression (i++).
• In a while or do...while loop, it jumps to the loop’s condition check.

Syntax

The syntax for a continue statement is simple:

continue;

Flow Diagram

You can visualize the flow of a loop with a continue statement as follows:

        ( Start Loop )
               |
               v
        +---------------+
        | Loop Condition|----(false)---->( End Loop )
        +---------------+
               |
             (true)
               |
               v
+---------------------------------+
|       Loop Body Code #1         |
+---------------------------------+
               |
               v
        +-----------------+
        | if (condition)  |----(true)----> (Jump to next iteration)
        +-----------------+               (bypassing code below)
               |
             (false)
               |
               v
+---------------------------------+
|       Loop Body Code #2         |
+---------------------------------+
               |
               v
     (Jump to next iteration)

Using continue in a for Loop

A common use case is to process only items that meet certain criteria. In this example, we use continue to skip even numbers and print only the odd ones.

// Goal: Print all odd numbers from 1 to 10.

for (int i = 1; i <= 10; i++)
{
    // If the number is even, skip the rest of this iteration.
    if (i % 2 == 0)
    {
        continue; // Proceed to the next value of i.
    }

    // This line is only reached for odd numbers.
    Console.WriteLine($"Odd number: {i}");
}

Console.WriteLine("Loop completed.");

Output

Odd number: 1
Odd number: 3
Odd number: 5
Odd number: 7
Odd number: 9
Loop completed.

Using continue in a while Loop

When using continue in a while or do...while loop, it’s crucial to ensure the loop’s control variable is updated before the continue statement to avoid an infinite loop.

// Goal: Print numbers from 10 to 19, but skip 15.
int a = 10;

while (a < 20)
{
    if (a == 15)
    {
        // IMPORTANT: Increment 'a' *before* continuing.
        // Otherwise, 'a' would always be 15, and the loop would never end.
        a++;
        continue;
    }

    Console.WriteLine($"Value of a: {a}");
    a++;
}

Output

Value of a: 10
Value of a: 11
Value of a: 12
Value of a: 13
Value of a: 14
Value of a: 16
Value of a: 17
Value of a: 18
Value of a: 19

Best Practices and Common Pitfalls

• Improving Readability: continue can sometimes make code cleaner than a deeply nested if statement. If the condition for skipping is simple, continue at the top of a loop can flatten the logic.
• The Infinite Loop Trap: The most common error is creating an infinite loop. In while and do-while loops, always make sure that the variable controlling the loop’s exit condition is modified before you call continue.
• foreach Loops: continue works seamlessly with foreach loops, making it an excellent tool for filtering collections during iteration.

Practical Example: Processing User Input

var inputs = new List<string> { "apple", "", "banana", "-1", "cherry" };
var validFruits = new List<string>();

foreach (var input in inputs)
{
    // Skip empty or invalid entries
    if (string.IsNullOrEmpty(input) || input == "-1")
    {
        Console.WriteLine($"Skipping invalid input: '{input}'");
        continue;
    }

    Console.WriteLine($"Processing valid fruit: {input}");
    validFruits.Add(input.ToUpper());
}

Console.WriteLine($"\nValid fruits processed: {string.Join(", ", validFruits)}");

Output

Processing valid fruit: apple
Skipping invalid input: ''
Processing valid fruit: banana
Skipping invalid input: '-1'
Processing valid fruit: cherry

Valid fruits processed: APPLE, BANANA, CHERRY