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

I know the question is old as hell, but I just had to solve the same problem, only for a very small set of strings(between 2 and 4).

In my case, I actually used manual lookup over an array of strings which turned up to be much faster than HashSet(I benchmarked it).

for (int i = 0; i < this.propertiesToIgnore.Length; i++)
{
    if (this.propertiesToIgnore[i].Equals(propertyName))
    {
        return true;
    }
}

Note, that it is better than hash set for only for tiny arrays!

EDIT: works only with a manual for loop, do not use LINQ, details in comments