如何从字符串中删除重复的子字符串

我希望通过你的问题本身通过改变句子来删除重复的单词和单词重复的字符。

using System;
using System.Collections.Generic;
using System.Linq;
namespace ConsoleApp
{
    internal class Program
    {
        private static void Main()
        {
            var input = new[] {"This is TEST TEST string", "shift+shift+shift+D"};
            foreach (string data in input)
            {
                bool contains = data.Contains((char)0x20);
                Console.WriteLine(contains ? StripFromSentence(data.TrimEnd(new[] {(char) 0x20})) : StripFromWord(data));
            }
            Console.ReadLine();
        }
        private static string StripFromWord(string word)
        {
            char[] chr = word.ToCharArray();
            var ap = new HashSet<char>();
            foreach (char s in chr)
                ap.Add(s);
            return ap.Aggregate(string.Empty, (current, c) => current + c);
        }
        private static string StripFromSentence(string sentence)
        {
            string[] strings = sentence.Split(new[] {(char) 0x20});
            var ap = new HashSet<string>();
            foreach (string s in strings)
                ap.Add(s);
            return ap.Aggregate(string.Empty, (current, word) => current + (word + (char)0x20));
        }
    }
}