title: How to check if a windows form already exists, open it if it does, creates a new one if it doesn't?
body: <p>I basically want something that does this:</p>
  
  <pre><code>if (form.isOpen() == true)
      form.ShowDialog();
  else
      form f = new form();
  </code></pre>
  
  <p>I have a form that displays a list of items added to an order, but when I go to another page and navigate back to make an order form it calls <code>form f = new form();</code>, which I believe resets the form. Any suggestions of how this can be overcome? </p>