title: Add comma to numbers every three digits using C#
body: <p>I want to add comma to decimal numbers every 3 digits using c#.<br>
  I wrote this code :</p>
  
  <pre><code>double a = 0; 
  a = 1.5;
  Interaction.MsgBox(string.Format("{0:#,###0}", a));
  </code></pre>
  
  <p>But it returns 2.<br>
  Where am I wrong ?<br>
  Please describe how can I fix it ?</p>