Regular Expression Language - Quick Reference

Imports System.Collections.Generic
Imports System.Globalization
Imports System.Text.RegularExpressions

Public Module Example
   Public Sub Demo(outputBlock As System.Windows.Controls.TextBlock)
      ' Define text to be parsed.
      Dim input As String = "Office expenses on 2/13/2008:" + vbCrLf + _
                            "Paper (500 sheets)                      $3.95" + vbCrLf + _
                            "Pencils (box of 10)                     $1.00" + vbCrLf + _
                            "Pens (box of 10)                        $4.49" + vbCrLf + _
                            "Erasers                                 $2.19" + vbCrLf + _
                            "Ink jet printer                        $69.95" + vbCrLf + vbCrLf + _
                            "Total Expenses                        $ 81.58" + vbCrLf
      ' Get current culture's DateTimeFormatInfo object.
      Dim nfi As NumberFormatInfo = CultureInfo.CurrentCulture.NumberFormat
      ' Assign needed property values to variables.
      Dim currencySymbol As String = nfi.CurrencySymbol
      Dim symbolPrecedesIfPositive As Boolean = CBool(nfi.CurrencyPositivePattern Mod 2 = 0)
      Dim groupSeparator As String = nfi.CurrencyGroupSeparator
      Dim decimalSeparator As String = nfi.CurrencyDecimalSeparator

      ' Form regular expression pattern.
      Dim pattern As String = Regex.Escape(CStr(IIf(symbolPrecedesIfPositive, currencySymbol, ""))) + _
                              "\s*[-+]?" + "([0-9]{0,3}(" + groupSeparator + "[0-9]{3})*(" + _
                              Regex.Escape(decimalSeparator) + "[0-9]+)?)" + _
                              CStr(IIf(Not symbolPrecedesIfPositive, currencySymbol, "")) 
      outputBlock.Text += "The regular expression pattern is: " + vbCrLf
      outputBLock.Text += "   " + pattern + vbCrLf      

      ' Get text that matches regular expression pattern.
      Dim matches As MatchCollection = Regex.Matches(input, pattern, RegexOptions.IgnorePatternWhitespace)               
      outputBlock.Text += String.Format("Found {0} matches. ", matches.Count) + vbCrLf

      ' Get numeric string, convert it to a value, and add it to List object.
      Dim expenses As New List(Of Decimal)

      For Each match As Match In matches
         expenses.Add(Decimal.Parse(match.Groups.Item(1).Value))      
      Next

      ' Determine whether total is present and if present, whether it is correct.
      Dim total As Decimal
      For Each value As Decimal In expenses
         total += value
      Next

      If total / 2 = expenses(expenses.Count - 1) Then
         outputBlock.Text += String.Format("The expenses total {0:C2}.", expenses(expenses.Count - 1))
      Else
         outputBlock.Text += String.Format("The expenses total {0:C2}.", total)
      End If   
   End Sub
End Module
' The example displays the following output:
'       The regular expression pattern is:
'          \$\s*[-+]?([0-9]{0,3}(,[0-9]{3})*\.?[0-9]+)
'       Found 6 matches.
'       The expenses total $81.58.

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Text.RegularExpressions;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Define text to be parsed.
      string input = "Office expenses on 2/13/2008:\n" + 
                     "Paper (500 sheets)                      $3.95\n" + 
                     "Pencils (box of 10)                     $1.00\n" + 
                     "Pens (box of 10)                        $4.49\n" + 
                     "Erasers                                 $2.19\n" + 
                     "Ink jet printer                        $69.95\n\n" + 
                     "Total Expenses                        $ 81.58\n"; 

      // Get current culture's DateTimeFormatInfo object.
      NumberFormatInfo nfi = CultureInfo.CurrentCulture.NumberFormat;
      // Assign needed property values to variables.
      string currencySymbol = nfi.CurrencySymbol;
      bool symbolPrecedesIfPositive = nfi.CurrencyPositivePattern % 2 == 0;
      string groupSeparator = nfi.CurrencyGroupSeparator;
      string decimalSeparator = nfi.CurrencyDecimalSeparator;

      // Form regular expression pattern.
      string pattern = Regex.Escape( symbolPrecedesIfPositive ? currencySymbol : "") + 
                       @"\s*[-+]?" + "([0-9]{0,3}(" + groupSeparator + "[0-9]{3})*(" + 
                       Regex.Escape(decimalSeparator) + "[0-9]+)?)" + 
                       (! symbolPrecedesIfPositive ? currencySymbol : ""); 
      outputBlock.Text += "The regular expression pattern is:\n";
      outputBlock.Text += "   " + pattern + "\n";      

      // Get text that matches regular expression pattern.
      MatchCollection matches = Regex.Matches(input, pattern, RegexOptions.IgnorePatternWhitespace);               
      outputBlock.Text += String.Format("Found {0} matches.\n", matches.Count); 

      // Get numeric string, convert it to a value, and add it to List object.
      List<decimal> expenses = new List<Decimal>();

      foreach (Match match in matches)
         expenses.Add(Decimal.Parse(match.Groups[1].Value));      

      // Determine whether total is present and if present, whether it is correct.
      decimal total = 0;
      foreach (decimal value in expenses)
         total += value;

      if (total / 2 == expenses[expenses.Count - 1]) 
         outputBlock.Text += String.Format("The expenses total {0:C2}.", expenses[expenses.Count - 1]);
      else
         outputBlock.Text += String.Format("The expenses total {0:C2}.", total);

   }  
}
// The example displays the following output:
//       The regular expression pattern is:
//          \$\s*[-+]?([0-9]{0,3}(,[0-9]{3})*\.?[0-9]+)
//       Found 6 matches.
//       The expenses total $81.58.