C#: What is the difference between HashSet<T> and SortedSet<T>?

HashSet<T> — unordered. SortedSet<T> — sorted.

HashSet:

• Unordered.
• O(1) operations.
• Faster.

SortedSet:

• Sorted.
• O(log n) operations.
• Range queries.

1// HashSet
2var set = new HashSet<int> { 3, 1, 2 };
3// Iteration: 3, 1, 2 (unordered)
4
5// SortedSet
6var sorted = new SortedSet<int> { 3, 1, 2 };
7// Iteration: 1, 2, 3 (sorted)

Key: HashSet for fast lookup, SortedSet for order.