title: How to add property to existing Winforms control
body: <p>I'm not sure if this is even possible. I've done some research, but haven't been able to find anything conclusive. There is a similar question <a href="https://stackoverflow.com/questions/11382323/add-attach-property-to-existing-control">here</a>, but it's for WPF.</p>
  
  <p>What I'd like to do is add a custom property to an existing WinForms GroupBox (or any control) on my form. For this example we'll use "Link". Say each GroupBox in my program contains a hyperlink, and then all I would need to do when I start my program is do this:</p>
  
  <pre><code>MyGroupBox.Link = "http:\\www.google.com\"
  </code></pre>
  
  <p>Later in my program I could set my hyperlink content to refer to <code>MyGroupBox.Link</code>. </p>
  
  <p>Is it possible to manipulate a Winforms control like this? I'd rather not make a custom control if I don't have to.</p>
  
  <p>I saw from <a href="https://stackoverflow.com/questions/8927800/how-can-i-add-new-existing-property-to-my-control">this question</a> that I could extend my control, but how I would that look in my particular case? Is that the same as creating a custom control?</p>