Regex with vb.net

Question

I have the following html contained in a string.

<tr>
   <td>Hello</td>
</tr>
<tr>
   <td>World</td>
</tr>
<tr>
   <td>lets all smile</td>
</tr>

I would like to use RegEx to find the <tr></tr> that contains the text "World". The difficulty is that there might be other <td> around the one that contains the search text. So we need to be able to search for the <tr> and </tr> nearest to the search text with any text between the <tr> and the search text.

The result of the match would be.

<tr>
<td>World</td>
</tr>

I'm using vb.net by the way.

Could anyone help at all?

Thanks

Richard

you could have easily typed html (instead of > <) by selecting and formatting it with ctrl-k — Amarghosh
– Amarghosh, Commented Dec 8, 2009 at 10:24
Read this blog post from our benevolent leader: codinghorror.com/blog/archives/001311.html — Hans Passant
– Hans Passant, Commented Dec 8, 2009 at 15:47

David Hedlund · Accepted Answer · 2009-12-08 10:15:11Z

6

First of all, it should be pointed out that you want to use the HTML Agility Pack, and not regex, for this kind of things.

But other than that, a pattern could look like:

(<tr>.*?World.*?</tr>)

It's a rather lousy pattern, but then again, use the agility pack.

answered Dec 8, 2009 at 10:15

David Hedlund

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9 Comments

Amarghosh Over a year ago

wouldn't this match the first 6 lines - from first <tr> to the </tr> after World?

David Hedlund Over a year ago

No, the non-greedy operators ? will make sure the whitespace between <tr> and World is kept as small as possible, without breaking the match

Amarghosh Over a year ago

Tested on Expresso and got this. <tr><td>Hello</td></tr><tr><td>World</td></tr>

Amarghosh Over a year ago

That is not how non-greediness work. Non greediness is responsible for not matching the whole string (including the last </tr>) - after all the whole string starts with <tr> and ends with </tr> - but due to the .*? at the end of regex, it matches the first </tr>

David Hedlund Over a year ago

cool, i managed to reproduce the same actually. so the pattern could be rewritten (something quick and dirty would be (<tr>[^<]*<td>World.*?</tr>)), but more importantly, my main point in my reply was for expressions such as these not to be used

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