C# For Loop

Last modified on: October 19, 2024

<h3>C# For Loop: Efficiently Repeating Code with a Defined Number of Iterations</h3>
<p>In C#, the <code>for</code> loop is a control structure that allows you to repeatedly execute a block of code a certain number of times. It is typically used when the number of iterations is known beforehand, such as when iterating through arrays or performing calculations over a fixed range.</p>
<hr />
<h3>1. <strong>Basic Syntax of a For Loop</strong></h3>
<p>The <code>for</code> loop has three parts:</p>
<ol>
<li><strong>Initialization</strong>: Sets the starting point of the loop.</li>
<li><strong>Condition</strong>: Defines the condition that must be <code>true</code> for the loop to continue.</li>
<li><strong>Iteration</strong>: Defines how the loop variable changes after each iteration.</li>
</ol>
<h4>Syntax:</h4>
<pre class="language-csharp"><code>for (initialization; condition; iteration)
{
    // Code to be executed on each iteration
}
</code></pre>
<p>&nbsp;</p>
<ul>
<li><strong>Initialization</strong>: Executed once at the beginning of the loop.</li>
<li><strong>Condition</strong>: Checked before each iteration. If it evaluates to <code>true</code>, the loop runs.</li>
<li><strong>Iteration</strong>: Executed at the end of each iteration to update the loop variable.</li>
</ul>
<hr />
<h3>2. <strong>Example of a Simple For Loop</strong></h3>
<p>The following loop prints numbers from 1 to 5:</p>
<pre class="language-csharp"><code>for (int i = 1; i &lt;= 5; i++)
{
    Console.WriteLine(i);
}
</code></pre>
<p>&nbsp;</p>
<p><strong>Output:</strong></p>
<pre class="language-csharp"><code>1
2
3
4
5
</code></pre>
<p>&nbsp;</p>
<p>In this example:</p>
<ul>
<li>The loop starts with <code>i = 1</code>.</li>
<li>The condition <code>i &lt;= 5</code> ensures the loop continues as long as <code>i</code> is less than or equal to 5.</li>
<li>After each iteration, <code>i</code> is incremented by <code>1</code> (<code>i++</code>).</li>
</ul>
<hr />
<h3>3. <strong>Reverse For Loop (Counting Down)</strong></h3>
<p>You can also use a <code>for</code> loop to count in reverse by decrementing the loop variable.</p>
<h4>Example:</h4>
<pre class="language-csharp"><code>for (int i = 5; i &gt; 0; i--)
{
    Console.WriteLine(i);
}
</code></pre>
<p>&nbsp;</p>
<p><strong>Output:</strong></p>
<pre class="language-csharp"><code>5
4
3
2
1
</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 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"><hr />
<h3>4. <strong>For Loop with Multiple Variables</strong></h3>
<p>The <code>for</code> loop allows you to initialize and update multiple variables at once.</p>
<h4>Example:</h4>
<pre class="language-csharp"><code>for (int i = 1, j = 10; i &lt;= 5; i++, j--)
{
    Console.WriteLine("i: " + i + ", j: " + j);
}
</code></pre>
<p>&nbsp;</p>
<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>i: 1, j: 10
i: 2, j: 9
i: 3, j: 8
i: 4, j: 7
i: 5, j: 6
</code></pre>
</div>
<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">
<p>Here, <code>i</code> is incremented while <code>j</code> is decremented in each iteration.</p>
<hr />
<h3>5. <strong>Breaking Out of a For Loop</strong></h3>
<p>You can use the <code>break</code> statement to exit a <code>for</code> loop early, regardless of the condition.</p>
<h4>Example:</h4>
<pre class="language-csharp"><code>for (int i = 1; i &lt;= 10; i++)
{
    if (i == 5)
    {
        break;  // Exit the loop when i is 5
    }
    Console.WriteLine(i);
}
</code></pre>
<p><strong>Output:</strong></p>
<pre class="language-csharp"><code>1
2
3
4
</code></pre>
<p>When <code>i</code> reaches 5, the <code>break</code> statement terminates the loop.</p>
<hr />
<h3>6. <strong>Skipping an Iteration with <code>continue</code></strong></h3>
<p>The <code>continue</code> statement skips the rest of the current iteration and proceeds to the next one.</p>
<h4>Example:</h4>
<pre class="language-csharp"><code>for (int i = 1; i &lt;= 5; i++)
{
    if (i == 3)
    {
        continue;  // Skip the current iteration when i is 3
    }
    Console.WriteLine(i);
}
</code></pre>
<p><strong>Output:</strong></p>
<pre class="language-csharp"><code>1
2
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">
<p>When <code>i</code> is 3, the loop skips that iteration and continues with the next one.</p>
<hr />
<h3>7. <strong>Nested For Loops</strong></h3>
<p>You can use a <code>for</code> loop inside another <code>for</code> loop to handle more complex scenarios, such as working with multidimensional arrays.</p>
<h4>Example: Multiplication Table</h4>
<pre class="language-csharp"><code>for (int i = 1; i &lt;= 5; i++)
{
    for (int j = 1; j &lt;= 5; j++)
    {
        Console.Write((i * j) + "\t");
    }
    Console.WriteLine();
}
</code></pre>
<p><strong>Output:</strong></p>
<pre class="language-csharp"><code>1   2   3   4   5   
2   4   6   8   10  
3   6   9   12  15  
4   8   12  16  20  
5   10  15  20  25  
</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">
<p>In this example, the outer loop controls the rows, while the inner loop controls the columns.</p>
<hr />
<h3>8. <strong>For Loop with Arrays</strong></h3>
<p>A common use case for the <code>for</code> loop is iterating through the elements of an array.</p>
<h4>Example:&nbsp;</h4>
<pre class="language-csharp"><code>int[] numbers = { 1, 2, 3, 4, 5 };

for (int i = 0; i &lt; numbers.Length; i++)
{
    Console.WriteLine(numbers[i]);
}
</code></pre>
<p><strong>Output:</strong></p>
<pre class="language-csharp"><code>1
2
3
4
5
</code></pre>
<p>Here, the <code>for</code> loop iterates over each element of the array and prints it.</p>
<hr />
<h3>9. <strong>For Each Loop (Alternative to For Loop)</strong></h3>
<p>In C#, the <code>foreach</code> loop provides a simpler syntax for iterating over collections (like arrays) without needing to manage loop counters.</p>
<h4>Example:</h4>
<pre class="language-csharp"><code>int[] numbers = { 1, 2, 3, 4, 5 };

foreach (int number in numbers)
{
    Console.WriteLine(number);
}
</code></pre>
<p>The <code>foreach</code> loop is often more readable when you don't need to modify the loop counter manually.</p>
<hr />
<h3>10. <strong>For Loop vs. While Loop</strong></h3>
<p>Both <code>for</code> and <code>while</code> loops are used for repetition, but they are suited for different scenarios:</p>
<ul>
<li>Use a <strong><code>for</code> loop</strong> when you know how many times the loop should run.</li>
<li>Use a <strong><code>while</code> loop</strong> when the loop continues until a condition changes, but the number of iterations isn't predetermined.</li>
</ul>
<hr />
<h3>Conclusion</h3>
<p>The <code>for</code> loop in C# is an essential tool for writing efficient and readable code when the number of iterations is known in advance. It is versatile enough to handle arrays, nested loops, and multiple variables, making it one of the most commonly used control structures in programming.</p>
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