>>Also - instead of using Occurs() and the successive At(...., occurrence) which traverse the string many times (once for Occurs and each time for At)
>>consider using a RegEx that returns a matches collection. ( RegEx adds some overhead, but the string will be traversed once. It also lets you specify ignoreCase)
>
>RegEx is too specific to .NET. This one would cause too much problems when moving into another environment. We have found this was related to a very big string that the UCase() was not able to handle.

I think

(1) Every environment has a RegEx
(2) If you don't want to use it and avoid UCase() , String has an IndexOf() method that lets you ignore the case
http://msdn.microsoft.com/en-us/library/ms224424.aspx and http://msdn.microsoft.com/en-us/library/system.stringcomparison.aspx