using System;using System.Text.RegularExpressions;

public class Test{    //统计字符串中重复出现的单词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 jumped 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 jumped 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

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);      }   }}// The example displays the following output://       -42 is a currency value.//       19.99 is a currency value.//       0.001 is not a currency value.//       100 USD is not a currency value.//       .34 is a currency value.//       0.34 is a currency value.//       1,052.21 is not a currency value.//       $10.62 is a currency value.//       +1.43 is a currency value.//       -$0.23 is a currency value.