RegEx match to remove from string

Question

I need to remove #!# instances from string when there's not # before or after the instance.

For example...

LoremImpsum#!#Dolor => matches #!#

Lorem #!#ASD## => matches #!#

Lorem #!## => no match

Lorem##!# => no match

my code so far:

foreach (Match match in Regex.Matches(formattedHtml, @"(?<!#)(#!#)(?!#)")
    formattedHtml = formattedHtml.Replace(match.Value, "");

But it seems to me that negative lookahead or lookbehind wont work. Thanks.

Anu Viswan · Accepted Answer · 2020-01-06 00:43:03Z

1

It looks like you code fails in places where there are multiple occurrences and only one of them was supposed to be replaced.

Your Regex does it was supposed to do. However, the problem was with the Replace code. Instead of following

foreach (Match match in Regex.Matches(formattedHtml, @"(?<!#)(#!#)(?!#)")
 formattedHtml = formattedHtml.Replace(match.Value, "");

You should use

formattedHtml = Regex.Replace(formattedHtml,@"(?<!#)(#!#)(?!#)","");

According to your initial code, if it finds a match, it would replace all the occurances in the string even if it has a preceeding/succeeding '#'

answered Jan 5, 2020 at 13:25

Anu Viswan

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1 Comment

Man I feel like an idiot. I now understand what i did wrong... Thanks.