title: Format a Social Security Number (SSN) as XXX-XX-XXXX from XXXXXXXXX
body: <p>I am getting a social security number (SSN) from a data warehouse. While posting it to a CRM I want it to be formatted like <code>XXX-XX-XXXX</code> instead of <code>XXXXXXXXX</code>.</p>
  
  <p>It's like converting a simple string with dashes at positions <code>4</code> and <code>7</code>. I am pretty new to C#, so what is the best way to do this?</p>