C# Determine if List Has Duplicate

Unless I’m missing something, then you should be able to get away with something simple using Distinct(). Granted it won’t be the most complex implementation you could come up with, but it will tell you if any duplicates get removed:

var list = new List<string>();

// Fill the list

if(list.Count != list.Distinct().Count())
{
     // Duplicates exist
}