replacing an undefined tags inside an xml string using a regex.

Question

Hi!

i need to replace an undefined tags inside an xml string.

example: <abc> <>sdfsd <dfsdf></abc><def><movie></def> (only <abc> and <def> are defined)

should result with: <abc> &lt;&gt;sdfsd &lt;dfsdf&gt;</abc><def>&lt;movie&gt;<def> <> and <dfsdf> are not predefined as and and does not have a closing tag.

it must be done with a regex!. no using xml load and such.

i'm working with C# .Net

Thanks!

Answer 1

it must be done with a regex! no using xml load and such.

I must hammer this nail in with my boot! No using a hammer and such. It's an old story :)

You'll need to supply more information. Are "valid" tags allowed to be nested? Are the "valid" tags likely to change at any point? How robust does this need to be?

Assuming that your list of valid tags isn't going to change at any point, you could do it with a regex substitution:

s/<(?!\/?(your|valid|tags))([^>]*)>/&lt;$1&gt;/g

Answer 2

How about this:

    string s = "<abc> <>sdfsd <dfsdf></abc><def><movie></def>";
    string regex = "<(?!/?(?:abc|def)>)|(?<!</?(?:abc|def))>";
    string result = Regex.Replace(s, regex, match =>
    {
        if (match.Value == "<")
            return "&lt;";
        else
            return "&gt;";
    });
    Console.WriteLine(result);

Result:

<abc> &lt;&gt;sdfsd &lt;dfsdf&gt;</abc><def>&lt;movie&gt;</def>

Also, when tested on your other test case (which by the way I found in a comment on the other question):

<abc>>sdfsdf<<asdada>>asdasd<>asdasd<asdsad>asds<</abc>

I get this result:

<abc>&gt;sdfsdf&lt;&lt;asdada&gt;&gt;asdasd&lt;&gt;asdasd&lt;asdsad&gt;asds&lt;</abc>

Let me guess... this doesn't work for you because you just thought of a new requirement? ;)