title: In c# how to use String.Format for a number and pad left with zeros so its always 6 chars
body: <p>I want to use c# format to do this:</p>
  
  <p>6 = "000006"<br />
  999999 = "999999"<br />
  100 = "000100"<br />
  -72 = error<br />
  1000000 = error<br /></p>
  
  <p>I was trying to use String.Format but without success. </p>