Performance is greatly improved if we can create the index in memory.
We preserve the ability to create the index using files for recovery in
low resource environments.
After we removed the tilde expansion in revision c9aa6cf5fb ("Avoid
performing tilde expansion"), the Utility.ExpandEnvironmentVariables
method simply called System.Environment.ExpandEnvironmentVariables. We
can simplify the code by just referencing the built-in method directly.
InvariantCulture is useful when comparing / sorting human language strings in a culturely correct way. It handles things like accented letters in a way that makes sense to humans (e.g., 'a' should be sorted next to 'á', rather than after 'z').
Ordinal looks just at the raw code points of the characters. As such, it is recommended for use in cases when comparing system strings (file paths, command line parameters, config settings, etc.). Since it doesn't need to use the culture specific sorting rules, this method can often be faster.
For more information, see https://stackoverflow.com/questions/492799/difference-between-invariantculture-and-ordinal-string-comparison (and other related questions)
Kenneth Skovhede