Check out example codes for "c# find duplicates in list of strings". It will help you in understanding the concepts better.

Code Example 1

var list = new List<string>();

// Fill the list

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

Code Example 2

var list = new List<string>();
list.GroupBy(n => n).Any(c => c.Count() > 1);

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