Simple permutation algorithm

I'm trying to create a simple permutation algorithm where you pass any number eg 123 and it should return the largest number without repeating. I tried something of this type more when I step 4242 it does not return me 4422 but 4242 as larger.

 static void ComparacoesPossiveis(ref int entrada, out int saida)
        {
            saida = 1;
            for (int i = 1; i <= entrada; i++)
            {
                saida *= i;
            }
        }

        public static void teste(int number)
        {
            if (number >= 10000000)
            {
                Console.WriteLine(-1);
                Console.ReadKey();
                return;
            }

            var array = number.ToString().ToArray();

            int tamanhoArray = array.Length;
            int[] vetor = new int[tamanhoArray];
            int[] temp = new int[tamanhoArray];
            int[] vetTmp = new int[tamanhoArray];

            for (int i = 0; i < tamanhoArray; i++)
            {
                vetor[i] = Convert.ToInt32(array[i].ToString());
            }

            int y, x;
            y = vetor.Length;
            ArrayList combinacoes = new ArrayList();

            ComparacoesPossiveis(ref y, out x);

            while (x > 0)
            {
                for (int j = 0; j < y - 1; j++)
                {

                    string numero = "";

                    vetTmp[j] = vetor[j];
                    vetor[j] = vetor[j + 1];
                    vetor[j + 1] = vetTmp[j];


                    for (int i = 0; i < vetor.Length; i++)
                        numero += vetor[i].ToString();

                    combinacoes.Add(Convert.ToInt32(numero));
                }
                x -= y;
            }

            combinacoes.Sort();

            Console.WriteLine("O maior numero é " + combinacoes[combinacoes.Count - 1].ToString());
            Console.ReadKey();
        }