((an)|(in)|(on))
using System; using System.Text.RegularExpressions; public class MainClass { public static void Main() { Regex p = new Regex("((an)|(in)|(on))"); MatchCollection mn = p.Matches("King, Kong Kang"); for (int i = 0; i < mn.Count; i++) { Console.WriteLine("Found '{0}' at position {1}",mn[i].Value, mn[i].Index); } } }