.NET collection that throws an exception when a duplicate is added

Question

Is there a collection (apart from Dictionary) in the .NET framework (3.5) that throws an exception when a duplicate is added?

HashSet does not throw an exception here:

HashSet<string> strings = new HashSet<string>();
strings.Add("apple");
strings.Add("apple");

Whereas the Dictionary does:

Dictionary<string, string> dict = new Dictionary<string, string>();
dict.Add("dude", "dude");
dict.Add("dude", "dude"); //throws exception

EDIT: Is there a collection without (Key, Value) that does this? I also want AddRange if possible...

I rolled my own:

public class Uniques<T> : HashSet<T>
{

    public Uniques()
    { }

    public Uniques(IEnumerable<T> collection)
    {
        AddRange(collection);
    }

    public void Add(T item)
    {
        if (!base.Add(item))
        {
            throw new ArgumentException("Item already exists");
        }
    }


    public void AddRange(IEnumerable<T> collection)
    {
        foreach (T item in collection)
        {
            Add(item);
        }
    }
}

Answer 1

But the HashSet.Add method returns false if the value already is present - isn't that enough?

HashSet<string> set = new HashSet<string>();
...
if (!set.Add("Key"))
    /* Not added */