Как я могу написать функцию, возвращающую все анаграммы данного слова (включая само слово) в любом порядке.

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An anagram is a word formed from another by rearranging its letters, using all the original letters exactly once; for example, orchestra can be rearranged into carthorse.

Write a function which returns all anagrams of a given word (including the word itself) in any order.

For example GetAllAnagrams("abba") should return collection containing "aabb", "abab", "abba", "baab", "baba", "bbaa".

using System;

using System.Text;

using System.Collections.Generic;

public class AllAnagrams

{

public static ICollection<string> GetAllAnagrams(string str)
{

throw new NotImplementedException("Waiting to be implemented.");

}

public static void Main(string[] args)

{

ICollection<string> anagrams = GetAllAnagrams("abba"); foreach (string a in anagrams)

Console.WriteLine(a);

}
}

Что я уже пробовал:

using System;
using System.Collections.Generic;

public class AllAnagrams
{
	public static ICollection<string> GetAllAnagrams(string str)
	{
		List<string> _List = new List<string>();
		bool[] noswitch = new bool[str.Length];
		getOptions(str, ref noswitch, ref _List, str.Length);
		ICollection<string> list = _List;
		return list;
	}

	public void getOptions(string word, ref bool[] noswitch, ref List<string> options, int size)
	{
		if (size > 2)
		{
			for (int i = 0; i < noswitch.Length; i++)
			{
				noswitch[i] = true;
				getOptions(word, ref noswitch, size - 1);
				noswitch[i] = false;
			}
		}
		else
		{
			for (int y = 0; y < noswitch.Length; y++)
			{
				int prevCount = -1;
				if (noswitch[y] == false)
				{
					if (prevCount == -1)
					{
						prevCount = y;
					}
					else
					{
						char[] array = word.ToCharArray();
						char charb = word[y];
						array[y] = array[prevCount];
						array[prevCount] = charb;
						string newWord = new string (array);
						if (!options.Contains(newWord))
						{
							options.Add(newWord);
							Console.WriteLine("added");
						}
					}
				}
			}
		}
	}

	public static void Main(string[] args)
	{
		ICollection<string> anagrams = GetAllAnagrams("abba");
		foreach (string a in anagrams)
			Console.WriteLine(a);
	}
}

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