Test if all values in a list are unique

Question

I have a small list of bytes and I want to test that they\'re all different values. For instance, I have this:

List theList = new List

        

Answer 1

Here's another approach which is more efficient than Enumerable.Distinct + Enumerable.Count (all the more if the sequence is not a collection type). It uses a HashSet which eliminates duplicates, is very efficient in lookups and has a count-property:

var distinctBytes = new HashSet(theList);
bool allDifferent = distinctBytes.Count == theList.Count;

or another - more subtle and efficient - approach:

var diffChecker = new HashSet();
bool allDifferent = theList.All(diffChecker.Add);

HashSet.Add returns false if the element could not be added since it was already in the HashSet. Enumerable.All stops on the first "false".