title: Auto Generate alphanumeric Unique Id with C#
body: <p>Total string length is 5 chars</p>
  
  <p>I have a scenario, ID starts with </p>
  
  <p>A0001 and ends with A9999 then
  B0001 to B9999  until F0001 to f9999</p>
  
  <p>after that</p>
  
  <p>FA001 to FA999 then
  FB001 to FB999  until ....FFFF9</p>
  
  <p>Please suggest any idea on how to create this format.</p>