//引入命名空间
using System;
using System.Text.RegularExpressions;

public class Test
{

    public static void Main ()
    {

        // Define a regular expression for repeated words.
        Regex rx = new Regex(@"\b(?<word>\w+)\s+(\k<word>)\b",
          RegexOptions.Compiled | RegexOptions.IgnoreCase);

        // Define a test string.        
        string text = "The the quick brown fox  fox jumps over the lazy dog dog.";
        
        // Find matches.
        MatchCollection matches = rx.Matches(text);

        // Report the number of matches found.
        Console.WriteLine("{0} matches found in:\n   {1}", 
                          matches.Count, 
                          text);

        // Report on each match.
        foreach (Match match in matches)
        {
            GroupCollection groups = match.Groups;
            Console.WriteLine("'{0}' repeated at positions {1} and {2}",  
                              groups["word"].Value, 
                              groups[0].Index, 
                              groups[1].Index);
        }
    }
}
// The example produces the following output to the console:
//       3 matches found in:
//          The the quick brown fox  fox jumps over the lazy dog dog.
//       'The' repeated at positions 0 and 4
//       'fox' repeated at positions 20 and 25
//       'dog' repeated at positions 50 and 54

//引入命名空间
using System;
using System.Globalization;
using System.Text.RegularExpressions;

public class Example
{
   public static void Main()
   {
      // Get the current NumberFormatInfo object to build the regular 
      // expression pattern dynamically.
      NumberFormatInfo nfi = NumberFormatInfo.CurrentInfo;

      // Define the regular expression pattern.
      string pattern; 
      pattern = @"^\s*[";
      // Get the positive and negative sign symbols.
      pattern += Regex.Escape(nfi.PositiveSign + nfi.NegativeSign) + @"]?\s?";
      // Get the currency symbol.
      pattern += Regex.Escape(nfi.CurrencySymbol) + @"?\s?";
      // Add integral digits to the pattern.
      pattern += @"(\d*";
      // Add the decimal separator.
      pattern += Regex.Escape(nfi.CurrencyDecimalSeparator) + "?";
      // Add the fractional digits.
      pattern += @"\d{";
      // Determine the number of fractional digits in currency values.
      pattern += nfi.CurrencyDecimalDigits.ToString() + "}?){1}$";
      
      Regex rgx = new Regex(pattern);

      // Define some test strings.
      string[] tests = { "-42", "19.99", "0.001", "100 USD", 
                         ".34", "0.34", "1,052.21", "$10.62", 
                         "+1.43", "-$0.23" };

      // Check each test string against the regular expression.
      foreach (string test in tests)
      {
         if (rgx.IsMatch(test))
            Console.WriteLine("{0} is a currency value.", test);
         else
            Console.WriteLine("{0} is not a currency value.", test);
      }
   }
}

StreamReader sr = new StreamReader(filename);
string input;
string pattern = @"\b(\w+)\s\1\b";
while (sr.Peek() >= 0)
{
   input = sr.ReadLine();
   Regex rgx = new Regex(pattern, RegexOptions.IgnoreCase);
   MatchCollection matches = rgx.Matches(input);
   if (matches.Count > 0)
   {
      Console.WriteLine("{0} ({1} matches):", input, matches.Count);
      foreach (Match match in matches)
         Console.WriteLine("   " + match.Value);
   }
}
sr.Close();

StreamReader sr = new StreamReader(filename);
string input;
string pattern = @"\b(\w+)\s\1\b";
Regex rgx = new Regex(pattern, RegexOptions.IgnoreCase);

while (sr.Peek() >= 0)
{
   input = sr.ReadLine();
   MatchCollection matches = rgx.Matches(input);
   if (matches.Count > 0)
   {
      Console.WriteLine("{0} ({1} matches):", input, matches.Count);
      foreach (Match match in matches)
         Console.WriteLine("   " + match.Value);
   }
}
sr.Close();

//引入命名空间
using System;
using System.Text.RegularExpressions;

class MainClass
{
    public static void Main()
    {
        string s = "A, B,cCCC, D";
        Regex regex = new Regex(@" |, ");
        foreach (string sub in regex.Split(s))
        {
            Console.WriteLine("Word: {0}", sub);
        }
    }
}