What can I fix about this code to program it to display ONLY duplicates instead of with non-duplicates? Prompt for reference: Write a console app that inserts 30 random letters into a List. Perform the following queries on the List and display your results: [Hint: Strings can be indexed like arrays to access a character at a specific index.] Use LINQ to sort the List in ascending order. Use LINQ to sort the List in descending order. Display list with ONLY duplicates using System; using System.Collections.Generic; using System.Linq; using System.Text;

What can I fix about this code to program it to display ONLY duplicates instead of with non-duplicates?

Prompt for reference: 

Write a console app that inserts 30 random letters into a List<char>. Perform the following queries on the List and display your results: [Hint: Strings can be indexed like arrays to access a character at a specific index.]

Use LINQ to sort the List in ascending order.

Use LINQ to sort the List in descending order.

Display list with ONLY duplicates

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace List
{
    class Program
    {
        static void Main(string[] args)
        {

            //Create a Random object
            Random rand = new Random();

            //Create a List of type to store 30 random values
            List<char> list = new List<char>(30);

            //Generate a random number and insert a character into the list
            for (int i = 0; i < 30; i++)
            {
                int r = rand.Next(30) + 1;
                //insert letters that starts from 'a'
                list.Add((char)(r + 'a'));
            }

            Console.WriteLine("Before Sorting");
            //Print before sorting
            foreach (var item in list)
                Console.WriteLine("{0}", item);
            //Call OrderBy for each element in ascending order
            List<char> sortedList = list.OrderBy(n => n).ToList();

            Console.WriteLine("After ascending order sorting");

            //Print ascnding sorted list
            foreach (var item in sortedList )
                Console.WriteLine("{0}", item);

            //Call orderByDescending for each element
            List<char> decendingList = list.OrderByDescending(n => n).ToList();

            Console.WriteLine("After Descending order sorting");
            //Print decending sorted list
            foreach (var item in decendingList )
                Console.WriteLine("{0}", item);

            List<char> uniqueSortedList = sortedList.Distinct().ToList();
            
            

        }
    }
}