WHILE Loops

When to Use WHILE Loops

Use WHILE loops when you need to keep going until something happens.

Perfect for: Counting until target reached, asking until correct answer, adding until total is enough, repeating until user says stop.

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Example 1: Count to 5

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int count = 1;

while (count <= 5)
{
    Console.WriteLine($"Count: {count}");
    count++;
}

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Example 2: Keep Asking Until User Says "yes"

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string answer = "";

while (answer != "yes")
{
    Console.Write("Type 'yes' to continue: ");
    answer = Console.ReadLine();
}
Console.WriteLine("Thank you!");

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Example 3: Add Numbers Until Total Reaches 10

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int sum = 0;
int number = 1;

while (sum < 10)
{
    sum = sum + number;
    Console.WriteLine($"Added {number}, sum = {sum}");
    number++;
}

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Example 4: Print 4 Stars

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int counter = 0;

while (counter < 4)
{
    Console.Write("* ");
    counter++;
}
Console.WriteLine();

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Example 5: Keep Doubling Until Over 50

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int value = 1;

while (value <= 50)
{
    Console.WriteLine($"Value: {value}");
    value = value * 2;
}

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Example 6: Validate Team Name (Not Empty)

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bool isValidTeamName = false;
string teamName = Console.ReadLine();

while (!isValidTeamName)
{
    if (string.IsNullOrWhiteSpace(teamName))
    {
        Console.WriteLine("Team name cannot be empty. Please enter a valid team name.");
        teamName = Console.ReadLine();
    }
    else
    {
        isValidTeamName = true;
    }
}

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Example 7: Validate Number of Bricks (1 to 1000)

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bool isValidNumberOfBricks = false;
int numberOfBricks = 0;
string numberBriksInput = Console.ReadLine();

while (!isValidNumberOfBricks)
{
    if (!int.TryParse(numberBriksInput, out numberOfBricks) || numberOfBricks <= 0 || numberOfBricks > 1000)
    {
        Console.WriteLine("Please enter a valid positive integer for the number of bricks.");
        numberBriksInput = Console.ReadLine();
    }
    else
    {
        isValidNumberOfBricks = true;
    }
}

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Example 8: Validate Time Taken (Greater Than 0)

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bool isValidTimeTaken = false;
int timeTaken = 0;
string timeTakenInput = Console.ReadLine();

while (!isValidTimeTaken)
{
    if (!int.TryParse(timeTakenInput, out timeTaken) || timeTaken <= 0)
    {
        Console.WriteLine("Please enter a valid positive integer for the time taken.");
        timeTakenInput = Console.ReadLine();
    }
    else
    {
        isValidTimeTaken = true;
    }
}

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Example 9: Validate Judge Score (0 to 10)

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bool isValidScore = false;
float score = 0;
string scoreInput = Console.ReadLine();

while (!isValidScore)
{
    if (!float.TryParse(scoreInput, out score) || score < 0 || score > 10)
    {
        Console.WriteLine("Please enter a valid score between 0 and 10.");
        scoreInput = Console.ReadLine();
    }
    else
    {
        isValidScore = true;
    }
}

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Quick Reference

WHILE Loop Pattern

while (condition is true)
{
    // Keep doing this
}

Key points:

• Loop continues while the condition is true
• May not run at all if condition is initially false
• Make sure something inside changes the condition!