regex to find a string, excluding comments

You may use

(?<!^[p{Zs}t]*//.*)(?<!/*(?:(?!*/)[sSr])*?)bSQLHELPERb

Details

(?<!^[p{Zs}t]*//.*) – a negative lookbehind that fails the match if, immediately to the left of the current location, the following pattern does not match:
- ^ – start of line
- [p{Zs}t]* – any 0+ horizontal whitespaces
- // – a // substring
- .* – any 0+ chars other than line break chars
(?<!/*(?:(?!*/)[sSr])*?) – – a negative lookbehind that fails the match if, immediately to the left of the current location, the following pattern does not match:
- /* – a /* substring
- (?:(?!*/)[sSr])*? – (tempered greedy token) any char (matched with [sSr]), 0 or more repetitions but as few as possible (due to *?) that does not start a */ substring (due to the (?!*/) negative lookahead)
bSQLHELPERb – a whole word SQLHelper (b are word boundaries).