title: variable decimal places in .Net string formatters?
body: <p>Fixed decimal places is easy</p>
  
  <pre><code>String.Format("{0:F1}", 654.321);
  </code></pre>
  
  <p>gives </p>
  
  <pre><code>654.3
  </code></pre>
  
  <p>How do I feed the number of decimal places in as a parameter like you can in C? 
  So</p>
  
  <pre><code>String.Format("{0:F?}", 654.321, 2);
  </code></pre>
  
  <p>gives</p>
  
  <pre><code>654.32
  </code></pre>
  
  <p>I can't find what should replace the ?</p>