title: String format and hex chars
body: <p>can someone explain why this doesnt work:</p>
  
  <pre><code>string f = string.Format("\\x{0:00}{{0}}", 5);
  string o = string.Format(f, "INSERT TEXT");
  System.Diagnostics.Debug.WriteLine(f + " : " + o);
  </code></pre>
  
  <p>Output is:</p>
  
  <pre><code>\x05{0} : \x05INSERT TEXT
  </code></pre>
  
  <p>why does the \x05 not get replaced?</p>