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MatchEvaluator Delegate

Definition

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

public delegate string MatchEvaluator(Match match);
[System.Serializable]
public delegate string MatchEvaluator(Match match);

Parameters

match
Match

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

Return Value

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

Attributes

Examples

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.
      Console.WriteLine(sInput);

      // Replace matched characters using the delegate method.
      sInput = r.Replace(sInput, myEvaluator);
      
      // Write out the modified string.
      Console.WriteLine(sInput);
   }

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

Remarks

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.

Extension Methods

GetMethodInfo(Delegate)

Gets an object that represents the method represented by the specified delegate.

Applies to

Produkt Versionen
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 2.0, 2.1
UWP 10.0

See also