; order.id); 
</code></pre>
<p>Note: Result will be an <code>ILookup&lt;TKey,TElement&gt;</code>, which is a one-to-many dictionary that maps keys to collections of values.</p>
<h2 id="zip">Zip</h2>
<p>Zip creates an Enumerable of tuples, where the first element of the tuple is the element from the first sequence and the second element is the element from the second sequence.</p>
<pre><code class="language-csharp">int[] first = [1, 2, 3];
string[] second = [&quot;a&quot;, &quot;b&quot;, &quot;c&quot;];
//Re