FIX: The Regex class and the Match class may not correctly find matches for a regular expression

View products that this article applies to.

SYMPTOMS

When you use certain Regex patterns to search a regular expression, you can obtain incorrect results. For example, you expect the following two expressions to return the same results:

"([^{}]|\n)*"
""([^{}])*"

However, the first expression, "([^{}]|\n)*", does not return the correct results. The hotfix that this article describes resolves the problem.

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CAUSE

This problem occurs because of the way that the RegEx optimizer handles certain strings.

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A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next .NET Framework service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support (http://support.microsoft.com/contactus/?ws=support)

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

   Date         Time   Version            Size    File name
   -------------------------------------------------------------------------
   13-Jun-2003  01:32  1.0.3705.434       20,480  Perfcounter.dll  
   13-Jun-2003  10:58  1.0.3705.434    1,175,552  System.dll       
   13-Jun-2003  11:00  1.0.3705.434      311,296  System.runtime.remoting.dll  
   13-Jun-2003  11:01  1.0.3705.434      503,808  System.web.services.dll  
   13-Jun-2003  10:58  1.0.3705.434    1,302,528  System.xml.dll   
   13-Jun-2003  10:58  1.0.3705.434       65,536  Wsdl.exe

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STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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MORE INFORMATION

The Regex class represents an immutable (read-only) regular expression. It also contains static methods that permit the use of other regular expression classes without explicitly instantiating objects of the other classes.

The Match class represents the results of a regular expression matching operation. The following example uses the Match method of the Regex class to return an object of type Match in order to find the first match in the input string. The example uses the Match.Success property of the Match class to indicate whether a match was found.

The following code sample illustrates the behavior that this hotfix corrects:


using System;
using System.Text.RegularExpressions;
using System.Collections;

namespace brandon
{
	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	class Class1
	{
		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main(string[] args)
		{
			Regex r = new Regex("([^{}]|\n)*");

	
			MatchCollection mc = r.Matches(@"\n{\rtf1\ansi\ansicpg1252\uc1\deff0\stshfdbch0\stshfloch0\stshfhich0\stshfbi0\deflang1033\deflangfe1033
			
	hfjkdashfdlahdfjashkfjdhsajlkfdhsafd}")
IEnumerator e = mc.GetEnumerator();
	Match m = null;
			while (e.MoveNext())
			{
				m = (Match) e.Current;
				if (m.Success) 
				{
					// Print out the character position where a match was found. 
					// (Character position 3 in this case.)
					Console.WriteLine("Found match at position " + m.Index);
					Console.WriteLine("Length of match = " + m.Length);
					Console.WriteLine("Matching text = "+m.Value);
				}
				else
					Console.WriteLine("No match found");
			}
		}
	}
}

After you apply the hotfix, the strings are correctly identified as logically identical.

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