MatchEvaluator Delegate

MatchEvaluator Delegate


Represents the method that is called each time a regular expression match is found during a Replace method operation.

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

public delegate string MatchEvaluator(
	Match match


Type: System.Text.RegularExpressions.Match

The Match object that represents a single regular expression match during a Replace method operation.

Return Value

Type: System.String

A string returned by the method that is represented by the MatchEvaluator delegate.

You can use a MatchEvaluator delegate method to perform a custom verification or manipulation operation for each match found by a replacement method such as Regex.Replace(String, MatchEvaluator). For each matched string, the Replace method calls the MatchEvaluator delegate method with a Match object that represents the match. The delegate method performs whatever processing you prefer and returns a string that the Replace method substitutes for the matched string.

The following code example uses the MatchEvaluator delegate to replace every matched group of characters with the number of the match occurrence.

using System;
using System.Text.RegularExpressions;

class MyClass
   static void Main(string[] args)
      string sInput, sRegex;

      // The string to search.
      sInput = "aabbccddeeffcccgghhcccciijjcccckkcc";

      // A very simple regular expression.
      sRegex = "cc";

      Regex r = new Regex(sRegex);

      MyClass c = new MyClass();

      // Assign the replace method to the MatchEvaluator delegate.
      MatchEvaluator myEvaluator = new MatchEvaluator(c.ReplaceCC);

      // Write out the original string.

      // Replace matched characters using the delegate method.
      sInput = r.Replace(sInput, myEvaluator);

      // Write out the modified string.

   public string ReplaceCC(Match m)
   // Replace each Regex cc match with the number of the occurrence.
      return i.ToString() + i.ToString();		
   public static int i=0;
// The example displays the following output:
//       aabbccddeeffcccgghhcccciijjcccckkcc
//       aabb11ddeeff22cgghh3344iijj5566kk77

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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