title: Mask to format int 1, 10, 100, to string "001", "010", "100"
body: <p>How do I apply a mask to a string aiming to format the output text in the following fashion (at most 2 leading zeros):</p>
  
  <pre><code>int a = 1, b = 10, c = 100;
  string aF = LeadingZeroFormat(a), bF = LeadingZeroFormat(b), cF = LeadingZeroFormat(c);
  Console.Writeline("{0}, {1}, {2}", aF, bF, cF); // "001, 010, 100" 
  </code></pre>
  
  <p>What is the most elegant solution?</p>
  
  <p>Thanks in advance.</p>