Which collection in C# does not ❌ allow duplicate elements?

Which collection in C# does not ❌ allow duplicate elements? In C#, the HashSet collection does not allow duplicate elements. Explanation: HashSet is an unordered collection that stores unique elements. It internally uses a hash table to store items, ensuring that duplicate values cannot be added. When you try to add a duplicate element, it simply ignores it instead of throwing an error.