Regex Replace : Regex Replace « Regular Expression « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. Regular Expression
3. Regex Replace

using System;
using System.Text.RegularExpressions;
using System.Reflection;

  class Class1
  {
    [STAThread]
    static void Main(string[] args)
    {
            Regex cardExp = new Regex( @"(\d{4})-(\d{4})-(\d{4})-(\d{4})" );
            
            string safeOutputExp = "$1-xxxx-xxxx-$4";
            string cardNum;

            cardNum = "asdf-asdf-asdf-asdf";
        
            Console.WriteLine( cardExp.IsMatch( cardNum ) );
            Console.WriteLine( "Secure Output Result = {0}", cardExp.Replace( cardNum, safeOutputExp ));

            TestManualGrouping();
            CompileRegex( cardExp.ToString(), @"regexlib" );
    }
        
        static void CompileRegex( string exp, string assemblyName )
        {
            RegexCompilationInfo compInfo = new RegexCompilationInfo( exp, 0, "CreditCardExp", "", true );
            AssemblyName assembly = new AssemblyName();
            assembly.Name = assemblyName;

            RegexCompilationInfo[] rciArray = { compInfo };

            Regex.CompileToAssembly( rciArray, assembly );
        }

        static void TestManualGrouping()
        {
            Regex cardExp = new Regex( @"\d{4}" );
            string cardNum;

            cardNum = "asdf-asdf-asdf-asdf";

            if( cardExp.Matches( cardNum ).Count < 4 )
            {
                Console.WriteLine( "Invalid card number" );
                return;
            }

            foreach( Match field in cardExp.Matches( cardNum ))
            {
                if( field.Success == false )
                {
                    Console.WriteLine( "Invalid card number" );
                    return;
                }

                if( field.Index == 5 || field.Index == 10 )
                {
                    Console.WriteLine("-xxxx-");
                }
                else
                {
                    Console.WriteLine(field.Value);
                }
            }
        }
  }