String Comparison(C#)

When comparing programmatic strings, you should always use StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase. This is the fastest way to perform a comparison that is not to be affected in any linguistic way because culture information is not taken into account when performing the comparison.

On the other hand, when you want to compare strings in a linguistically correct manner (usually for display to an end user), you should use StringComparison.CurrentCulture or StringComparison.CurrentCultureIgnoreCase.

Reference: CLR Via C#