title: String Format Does Not Works For string
body: <p>I have a serial number which is String type.</p>
  
  <p>Like This;</p>
  
  <p>String.Format("{0:####-####-####-####}", "1234567891234567" );</p>
  
  <p>I need to see Like This, 1234-5678-9123-4567;</p>
  
  <p>Bu this Code does not work?</p>
  
  <p>Can you help me?</p>