I'm in my first six months of programming on the job and I'm still getting a feeling for standards and best practices.
When performing string or char comparison, is it more common to use ToUpper to compare uppercase characters or ToLower for lowercase? I've probably seen uppercase more often, but I was looking for a more definitive answer and maybe a long-winded optimization explanation (lower ASCII code, whatever).
Aside: In my current task, I'm using string#replace and my new string is going to be lowercase for readability, but does that necessarily mean I should use ToLower on both my source string and the substring that I'm looking for?
If there's a way to do a case-insensitive comparison without changing case you should use it instead. If not, in most situations it's better to convert to upper case. For example the German sharp-s ß converts to a double S in uppercase, and correctly compares equal to SS. If you converted to lower case this would fail since SS in lower case is ss, not ß.