C# While Loop

Last modified on: October 19, 2024

<h3>C# While Loop: Repeating Code with Conditional Loops</h3>
<p>The <code>while</code> loop in C# is a control flow statement that repeatedly executes a block of code as long as a specified Boolean condition remains <code>true</code>. It is useful when you don't know in advance how many times the loop will run but need it to continue based on a condition.</p>
<hr />
<h3>1. <strong>Basic Syntax of a While Loop</strong></h3>
<p>The <code>while</code> loop checks the condition before executing the loop body. If the condition evaluates to <code>true</code>, the loop body runs. If it evaluates to <code>false</code>, the loop terminates.</p>
<h4>Syntax:</h4>
<pre class="language-csharp"><code>while (condition)
{
    // Code to be executed repeatedly while the condition is true
}
</code></pre>
<hr />
<h3>2. <strong>Example of a Simple While Loop</strong></h3>
<p>In this example, a loop counts from 1 to 5 and prints each number.</p>
<pre class="language-csharp"><code>int i = 1;

while (i &lt;= 5)
{
    Console.WriteLine(i);
    i++;  // Increment the counter
}
</code></pre>
<p><strong>Output:</strong></p>
<pre class="language-csharp"><code>1
2
3
4
5
</code></pre>
<div class="dark bg-gray-950 contain-inline-size rounded-md border-[0.5px] border-token-border-medium relative">
<div class="flex items-center text-token-text-secondary bg-token-main-surface-secondary px-4 py-2 text-xs font-sans justify-between rounded-t-md h-9">&nbsp;</div>
</div>
<p>The loop runs while <code>i</code> is less than or equal to 5. Once <code>i</code> becomes 6, the condition <code>i &lt;= 5</code> becomes <code>false</code>, and the loop stops.</p>
<hr />
<h3>3. <strong>Infinite Loops</strong></h3>
<p>If the condition in a <code>while</code> loop never becomes <code>false</code>, the loop will run indefinitely, creating an infinite loop. You must ensure that your condition will eventually evaluate to <code>false</code> to avoid this.</p>
<h4>Example:</h4>
<pre class="language-csharp"><code>while (true)
{
    Console.WriteLine("This will run forever unless stopped.");
}
</code></pre>
<p>To break out of an infinite loop manually, you can use the <code>break</code> statement.</p>
<hr />
<h3>4. <strong>Using Break and Continue in While Loops</strong></h3>
<ul>
<li><strong><code>break</code>:</strong> Exits the loop immediately, regardless of the loop condition.</li>
<li><strong><code>continue</code>:</strong> Skips the rest of the current iteration and moves to the next iteration.</li>
</ul>
<h4>Example with <code>break</code>:</h4>
<pre class="language-csharp"><code>int i = 1;

while (i &lt;= 10)
{
    if (i == 5)
    {
        break;  // Exit the loop when i is 5
    }
    Console.WriteLine(i);
    i++;
}
</code></pre>
<p><strong>Output:</strong></p>
<div class="dark bg-gray-950 contain-inline-size rounded-md border-[0.5px] border-token-border-medium relative">
<div class="flex items-center text-token-text-secondary bg-token-main-surface-secondary px-4 py-2 text-xs font-sans justify-between rounded-t-md h-9">
<pre class="language-csharp"><code>1
2
3
4
</code></pre>
</div>
</div>
<h4>Example with <code>continue</code>:</h4>
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<pre class="language-csharp"><code>int i = 0;

while (i &lt; 5)
{
    i++;
    if (i == 3)
    {
        continue;  // Skip the rest of the loop when i is 3
    }
    Console.WriteLine(i);
}
</code></pre>
</div>
</div>
<p><strong>Output:</strong></p>
<div class="dark bg-gray-950 contain-inline-size rounded-md border-[0.5px] border-token-border-medium relative">
<div class="flex items-center text-token-text-secondary bg-token-main-surface-secondary px-4 py-2 text-xs font-sans justify-between rounded-t-md h-9">
<pre class="language-csharp"><code>1
2
4
5
</code></pre>
</div>
</div>
<p>When <code>i</code> is 3, the <code>continue</code> statement causes the loop to skip the <code>Console.WriteLine(i)</code> statement and move to the next iteration.</p>
<hr />
<h3>5. <strong>Do-While Loop (A Variation)</strong></h3>
<p>The <code>do-while</code> loop is similar to the <code>while</code> loop, but it ensures that the loop body is executed at least once, regardless of the condition. In a <code>do-while</code> loop, the condition is checked <strong>after</strong> the loop body has been executed.</p>
<h4>Syntax:</h4>
<pre class="language-csharp"><code>do
{
    // Code to be executed at least once
} while (condition);
</code></pre>
<p><strong>Example:</strong></p>
<pre class="language-csharp"><code>int i = 1;

do
{
    Console.WriteLine(i);
    i++;
} while (i &lt;= 5);
</code></pre>
<p><strong>Output:</strong></p>
<pre class="language-csharp"><code>1
2
3
4
5
</code></pre>
<hr />
<h3>6. <strong>Real-World Example: User Input</strong></h3>
<p>A common use case for a <code>while</code> loop is to continuously prompt the user for input until they provide valid data.</p>
<h4>Example:</h4>
<pre class="language-csharp"><code>int number;

while (true)
{
    Console.WriteLine("Enter a number between 1 and 10:");
    number = Convert.ToInt32(Console.ReadLine());

if (number &gt;= 1 &amp;&amp; number &lt;= 10)
    {
        break;  // Exit loop when the number is valid
    }
    else
    {
        Console.WriteLine("Invalid number. Please try again.");
    }
}

Console.WriteLine("You entered: " + number);
</code></pre>
<p>In this example, the loop continues to prompt the user until they enter a number within the range of 1 to 10.</p>
<hr />
<h3>7. <strong>While Loop vs. For Loop</strong></h3>
<p>Both <code>while</code> and <code>for</code> loops are used for repeating code, but they are preferred in different scenarios:</p>
<ul>
<li>Use a <strong><code>for</code> loop</strong> when you know how many iterations are needed in advance (e.g., counting from 1 to 10).</li>
<li>Use a <strong><code>while</code> loop</strong> when the number of iterations is unknown and depends on a condition (e.g., waiting for user input).</li>
</ul>
<hr />
<h3>Conclusion</h3>
<p>The <code>while</code> loop is a versatile and fundamental construct in C# for controlling the flow of your program based on a condition. It is especially useful when the number of iterations cannot be determined in advance. Properly managing loop conditions and using <code>break</code> and <code>continue</code> can help you avoid common pitfalls like infinite loops.</p>
<hr />
<h3>&nbsp;</h3>

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