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Editorial Team
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Asked: 2026-06-10T09:48:01+00:00

I have small problem. I try to write a function to extract something in

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I have small problem. I try to write a function to extract something in C# (I have to convert a regular expression from PHP to C#).

I generally write it like this:

public static class ExtensionMethods
{
  public String PregReplace(this String input, string[] pattern, string[] replacements)
  {
    for (var i = 0; i < pattern.Length; i++)
    {
        input = Regex.Replace(input, pattern[i], replacements[i]);
    }

    return input;
  }
}

But I have a problem with these examples (code in PHP)

preg_replace('@<head[^>]*?>.*?</head>@siu', ' ', $result);
preg_replace('@</?((frameset)|(frame)|(iframe))@iu', "\n\$0", $result);

But when I use this regulax expression in C#

String[] pattern = new String[2]{"@<head[^>]*?>.*?</head>@siu", "@</?((frameset)|(frame)|(iframe))@iu"};
String[] replace = new String[2]{" ", "\n\$0"};
input.PregReplace(pattern , replace );  //my new function

I don’t have any differences in input (I don’t catch a regular expression).
Can you help me with my function? Do I have error in regex?

EDIT:
I changed code to:

String[] pattern = new String[2]{"<head[^>]*?>.*?</head>", "</?((frameset)|(frame)|(iframe))"};
String[] replace = new String[2]{" ", "\n\\$0"};

input = "input = "><head><title>something</title></head><body>sdegsehgaeg<frame>aggsd</frame></";
string s = input.PregReplace(pattern, replace);

In answer I get

> <body>sdegsehgaeg
\<frame>aggsd
\</frame></

It is

> <body>sdegsehgaeg\n\\<frame>aggsd\n\\</frame></

This is only to much char \ for \n\$0. If I change \n\$0 to \n\$0 I get error (urecognized escape sequence)

Ok I solved problem (\n$0)

Thank you for help.

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1 Answer

  1. Editorial Team

    Remove the @ in your code, and the siu and iu after your last @. In php you need those modifiers, in C# you would call some RegexOptions if necessary.

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