using System; using System.Text.RegularExpressions; public class Test { public static void Main() { string[] data = {"TE33", "FR56", "not", "blahblahAJ00blah"}; foreach(string myString in data) { if(Regex.IsMatch(myString, "^[A-Za-z]{2}[0-9]{2}$")) { Console.WriteLine("{0} matches", myString); } else { Console.WriteLine("{0} doesn't match", myString); } } } }