RegEx match a phrase but Replace only inner part

Posted on 2009-06-29
Last Modified: 2012-05-07
Please look at the example code:

Const word_separation_chars As String = "^A-Z !#"
Dim search_str As String = "HELLO"
Dim reg_str As String = String.Format("([{0}]{1}[{0}])", word_separation_chars, search_str)

Dim input_line As String = " !HELLO WORLD# "
Dim marked_line As String = Regex.Replace(input_line, reg_str, "<span>$1</span>")

Will result:
" <span>!HELLO<span> WORLD# "

But what I need is to capture only the "HELLO" part (without the separation character) i.e.:
" !<span>HELLO<span> WORLD# "

How should I do that elegantly?
Thanks, Aryeh.
Question by:tuchfeld
  • 2
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Author Comment

ID: 24740194
Note that the search_str can apear several times inside the input_line.
LVL 39

Accepted Solution

abel earned 250 total points
ID: 24740539
what have now is:

Regex.Replace(input_line, "([^A-Z !#]HELLO[[^A-Z !#])", "<span>$1</span>")
you can change that to the following:

Regex.Replace(input_line, "([^A-Z !#])(HELLO)([[^A-Z !#])", "$1<span>$2</span>$3")
Or, in other words, in your third line:

Dim reg_str As String = String.Format("([{0}])({1})([{0}])", word_separation_chars, search_str)

-- Abel --
LVL 39

Expert Comment

ID: 24740544
> Note that the search_str can apear several times inside the input_line.
that doesn't matter, it will automatically replace all occurrences for each time the whole regex is matched.

Author Comment

ID: 24743035
FYI, if anyone might find it useful, here is the RegEx I eventually used (it includes match at the beginning and end of input).
Const word_separation_chars As String = "^a-z"
Dim reg_str As String = String.Format("((^|[{0}])({1})([{0}]|$))", word_separation_chars, search_str)

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