Functional .NET - Fighting Friction in the BCL with Directory.GetFiles

The Issues There are several issues that lead me to come up with an alternative for this situation of getting all files in a directory. Arrays shouldn't be returned from method calls Processor intensive for iterating over large directory trees instead of calculating only what I need, when I need it Filtering is weak, and only uses file format patterns Access denied internal messages occur for no apparent reason which halts the method