title: Array.Add vs +=
body: <p>I've found some interesting behaviour in PowerShell Arrays, namely, if I declare an array as:</p>
  
  <pre><code>$array = @()
  </code></pre>
  
  <p>And then try to add items to it using the <code>$array.Add("item")</code> method, I receive the following error:</p>
  
  <blockquote>
    <p>Exception calling "Add" with "1" argument(s): "Collection was of a fixed size."</p>
  </blockquote>
  
  <p>However, if I append items using <code>$array += "item"</code>, the item is accepted without a problem and the "fixed size" restriction doesn't seem to apply.</p>
  
  <p>Why is this?</p>