In c# how to use String.Format for a number and pad left with zeros so its always 6 chars
<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>
