title: The <Out()> Attribute. What useful purpose does is serve?
body: <p>Under <code>System.Runtime.InteropServices</code> the <code>&lt;Out()&gt;</code> Attribute exists.
  But what is it for? I would be glad if you could use the following example as base for your answers.</p>
  
  <pre><code> Shared Sub Add(ByVal x As Integer, ByVal y As Integer, &lt;Out()&gt; ByRef Result As Integer)
    Result = x + y
   End Sub
  </code></pre>