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Regex.CompileToAssembly Method (RegexCompilationInfo[], AssemblyName)

Updated: February 2010

Compiles one or more specified Regex objects to a named file.

Namespace:  System.Text.RegularExpressions
Assembly:  System (in System.dll)

[HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)]
public static void CompileToAssembly(
	RegexCompilationInfo[] regexinfos,
	AssemblyName assemblyname


Type: System.Text.RegularExpressions.RegexCompilationInfo[]

An array that describes the regular expressions to compile.

Type: System.Reflection.AssemblyName

The file name of the assembly.


The value of the assemblyname parameter's AssemblyName.Name property is an empty or null string.


The regular expression pattern of one or more objects in regexinfos contains invalid syntax.


assemblyname or regexinfos is null.


The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: MayLeakOnAbort. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

The CompileToAssembly(RegexCompilationInfo[], AssemblyName) method generates a .NET Framework assembly in which each regular expression defined in the regexinfos array is represented by a class. Typically, the CompileToAssembly(RegexCompilationInfo[], AssemblyName) method is called from a separate application that generates an assembly of compiled regular expressions. Each regular expression included in the assembly has the following characteristics:

  • It is derived from the Regex class.

  • It is assigned the fully qualified name that is defined by the fullnamespace and name parameters of its corresponding RegexCompilationInfo object.

  • It has a default (or parameterless) constructor.

Ordinarily, the code that instantiates and uses the compiled regular expression is found in an assembly or application that is separate from the code that creates the assembly.

The following example creates an assembly named RegexLib.dll. The assembly includes two compiled regular expressions. The first, Utilities.RegularExpressions.DuplicatedString, matches two identical contiguous words. The second, Utilities.RegularExpressions.EmailAddress, checks whether a string has the correct format to be an e-mail address.

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

public class RegexCompilationTest
   public static void Main()
      RegexCompilationInfo expr;
      List<RegexCompilationInfo> compilationList = new List<RegexCompilationInfo>();

      // Define regular expression to detect duplicate words
      expr = new RegexCompilationInfo(@"\b(?<word>\w+)\s+(\k<word>)\b", 
                 RegexOptions.IgnoreCase | RegexOptions.CultureInvariant, 
      // Add info object to list of objects

      // Define regular expression to validate format of email address
      expr = new RegexCompilationInfo(@"^(?("")(""[^""]+?""@)|(([0-9A-Z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9A-Z])@))" + 
                 RegexOptions.IgnoreCase | RegexOptions.CultureInvariant, 
      // Add info object to list of objects

      // Generate assembly with compiled regular expressions
      RegexCompilationInfo[] compilationArray = new RegexCompilationInfo[compilationList.Count];
      AssemblyName assemName = new AssemblyName("RegexLib, Version=, Culture=neutral, PublicKeyToken=null");
      Regex.CompileToAssembly(compilationArray, assemName);                                                 

The regular expression that checks a string for duplicate words is then instantiated and used by the following example.

using System;
using Utilities.RegularExpressions;

public class CompiledRegexUsage
   public static void Main()
      string text = "The the quick brown fox  fox jumped over the lazy dog dog.";
      DuplicatedString duplicateRegex = new DuplicatedString(); 
      if (duplicateRegex.Matches(text).Count > 0)
         Console.WriteLine("There are {0} duplicate words in \n   '{1}'", 
            duplicateRegex.Matches(text).Count, text);
         Console.WriteLine("There are no duplicate words in \n   '{0}'", 
// The example displays the following output to the console: 
//    There are 3 duplicate words in 
//       'The the quick brown fox  fox jumped over the lazy dog dog.'

Successful compilation of this second example requires a reference to RegexLib.dll (the assembly created by the first example) to be added to the project.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0




February 2010

Replaced the regular expression pattern to validate an e-mail address.

Content bug fix.

May 2009

Added remarks and an example.

Customer feedback.