Validate address

   

using System;
using System.Text.RegularExpressions;

class RegexSubstitution
{
   public static void Main()
   {

      string text = "124 street";
      if ( !Regex.Match( text, @"^[0-9]+s+([a-zA-Z]+|[a-zA-Z]+s[a-zA-Z]+)$" ).Success ) {
         Console.WriteLine( "Invalid address");
      } 
   }
}