C# Determine Duplicate in List [duplicate]

Answer 1

Place all items in a set and if the count of the set is different from the count of the list then there is a duplicate.

bool hasDuplicates(List myList) {
    var hs = new HashSet();

    for (var i = 0; i < myList.Count; ++i) {
        if (!hs.Add(myList[i])) return true;
    }
    return false;
}

Should be more efficient than Distinct as there is no need to go through all the list.