Hello,
I've been using java for long time, and in java there are two interfaces - one for Set and one for SortedSet.
Set is a unique collection (you cannot add an item twice) and SortedSet is the same but sorted, you can add and find items quickly.
In c# all I found is Distionary and SortedDictionarty, but I it is not the same, I don't need the values, only the keys
I need these data structures. Is there a data structure I don't know about
thanks,

Set and Sorted Set
Yuki Chen