Please help making me do exceptions with random numbers : I've made this code for practicing and I want to make a list that keeps every numbers that this code wrote before so I dont want to get duplicates.
Sorry for my english

It's just guessing random numbers and I don't want it to guess the number that it already guessed before. 

Just to be clear I want to make it as a list


            int password = 432678;
            int valt = 999999;

                    for (int i = 0; i < valt; i++)
                    {
                        int[] test2 = new int[valt];

                        Random randNum = new Random();

                        for (int j = 0; j < test2.Length; j++)
                        {
                   
                            test2[i] = randNum.Next(1, valt);
                    
                   
                            Console.WriteLine("CURRENT: " + test2[i]);

                            

                            if (test2[i] == password)
                            {
                                goto Back;
                            }

                        }
                    }
  
        Back:
            Console.WriteLine("password: "+ password);
            Console.ReadLine();