title: c# I want to know if the first 3 characters in a string is letter?
body: <p>I'm developing a license plate number recognition system. The plate numbers in our county has a string length of 6-7. The first 2 or 3 character are  letters and the rest are numbers. </p>
  
  <p>I want to check when my system detect a object and recognize it then if the output has the format of 3 letters and followed by numbers.</p>