asp.net - How to replace special characters using regex -

using asp.net regex.

i've written extension method want use replace whole words - word might single special character '&'.

in case want replace '&' 'and', , i'll need use same technique reverse 'and' '&', must work whole words , not extended words 'hand'.

i've tried few variations regex pattern - started '\bword\b' didn't work @ ampersand, , have '\sword\s' works except removes spaces around word, meaning phrase "health & beauty" ends "healthandbeauty".

any appreciated.

here's extension method:

    public static string replaceword(this string @this,         string wordtofind,         string replacement,         regexoptions regexoptions = regexoptions.none)     {         guard.string.notempty(() => @this);         guard.string.notempty(() => wordtofind);         guard.string.notempty(() => replacement);          var pattern = string.format(@"\s{0}\s", wordtofind);          return regex.replace(@this, pattern, replacement, regexoptions);     } 

in order match dynamic string should enclosed spaces (or located @ start or end of string), can use negative lookaheads:

var pattern = string.format(@"(?<!\s){0}(?!\s)", wordtofind);                               ^^^^^^^   ^^^^^^        

or safer:

var pattern = string.format(@"(?<!\s){0}(?!\s)", regex.escape(wordtofind));                                                  ^^^^^^^^^^^^^  

the (?<!\s) lookbehind fail match if word not preceded non-whitespace character , (?!\s) lookahead fail match if word not followed non-whitespace character.