Best way to find out if IEnumerable<> has unique values

Question

I have a lot of code in which I do something like this

bool GetIsUnique(IEnumerable values)
{
    return values.Count() == values.Distinct().Count;
}
         


        

Answer 1

A quick way of finding the first duplicate, if present, is:

public static bool TryFindFirstDuplicate(this IEnumerable source, out T duplicate)
{
    var set = new HashSet();
    foreach (var item in source)
    {
        if (!set.Add(item))
        {
            duplicate = item;
            return true;
        }
    }
    duplicate = default(T);
    return false;
}