Best Collection for Fast String Lookup

Question

I need a list of strings and a way to quickly determine if a string is contained within that list.

To enhance lookup speed, I considered SortedList and

Answer 1

This sounds like a job for

 var keys = new HashSet();

Per MSDN: The Contains function has O(1) complexity.

But you should be aware that it does not give an error for duplicates when adding.