using System;
using System.Text.RegularExpressions;

class RegexSubstitution
{
   public static void Main()
   {

      string text = "124";
      if ( !Regex.Match( text, @"^d{5}$" ).Success )
      {
         Console.WriteLine( "Invalid zip code");
      }   
   }
}

           
          

   


using System;
using System.Text.RegularExpressions;

class RegexSubstitution
{
   public static void Main()
   {

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

           
          

   

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");
      } 
   }
}


           
          

   

using System;
using System.Text.RegularExpressions;

class RegexSubstitution
{
   public static void Main()
   {

      string text = "Name";
      if ( !Regex.Match(text,"^[A-Z][a-zA-Z]*$" ).Success )
      {
         Console.WriteLine( "Invalid last name");
      }

   }
}


           
          

using System;
using System.Text.RegularExpressions;

class RegexSubstitution
{
   public static void Main()
   {
      string testString1 = "1, 2, 3, 4, 5, 6, 7, 8";
      Regex testRegex1 = new Regex( @"d" );

      Console.WriteLine( "Original string: " + testString1 );

      String[] result = Regex.Split( testString1, @",s" );

      foreach ( string resultString in result )
         Console.WriteLine(""" + resultString + "", ");

   }
}

   


using System;
using System.Text.RegularExpressions;

class RegexSubstitution
{
   public static void Main()
   {
      string testString1 = "1, 2, 3, 4, 5, 6, 7, 8";
      Regex testRegex1 = new Regex( @"d" );

      Console.WriteLine( "Original string: " + testString1 );
      Console.WriteLine( "Replace first 3 digits by "digit": " + testRegex1.Replace( testString1, "digit", 3 ) );
   }
}

           
          

   


using System;
using System.Text.RegularExpressions;

class RegexSubstitution
{
   public static void Main()
   {
      string testString1 = "a b c stars *****";
      Regex testRegex1 = new Regex( @"d" );

      Console.WriteLine( "Original string: " + testString1 );
      Console.WriteLine( "Every word replaced by "word": " + Regex.Replace( testString1, @"w+", "word" ) );
      
   }
}