遍历列表以查找唯一字符C#

using System;
using System.Collections.Generic;

public class UniqueCharacterFinder
{
    public List<char> FindUniqueCharacters(List<char> characters)
    {
        List<char> uniqueCharacters = new List<char>();

        foreach (char c in characters)
        {
            if (!uniqueCharacters.Contains(c))
            {
                uniqueCharacters.Add(c);
            }
        }

        return uniqueCharacters;
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        List<char> characters = new List<char>() { 'a', 'b', 'c', 'a', 'b', 'd' };

        UniqueCharacterFinder finder = new UniqueCharacterFinder();
        List<char> uniqueCharacters = finder.FindUniqueCharacters(characters);

        Console.WriteLine("Unique characters:");
        foreach (char c in uniqueCharacters)
        {
            Console.WriteLine(c);
        }
    }
}