GeneratorVariants

using System;
using System.Collections.Generic;

namespace GeneratorVariants
{

    class Program
    {
        public static List<string> numTasks = new List<string>
        {
            "120",
            "121",
            "122",
            "123",
            "124",
            "125",
            "126",
            "127",
            "128",
            "129а",
            "120б",
            "120в",
            "120г",
            "120д",
            "120е",
            "120ж",
            "120з",
            "120и",
            "120к",
            "120л",
            "120м",
            "120н",
            "120о",
            "130а",
            "130б",
            "130в",
            "130г",
            "130д",
            "130е",
            "130ж",
            "130з",
            "130и",
            "130к",
            "130л",
            "130м",
            "130н",
            "130о",
            "130п",
            "130р",
            "131",
            "132",
            "133",
            "134",
            "135"
        };

        public static int countTasks = 5;
        public static int countVariants = 30;
        public static int[] indexTasks;
        static void Main(string[] args)
        {
            for (int i = 0; i < countVariants; i++) {
                indexTasks = new int[countTasks];
                Console.WriteLine($"Вариант {i+1}:");
                for (int j = 0; j < indexTasks.Length; j++)
                {
                    indexTasks[j] = ChoiseNum();
                    if (j == indexTasks.Length - 1)
                        Console.Write($"{numTasks[indexTasks[j]]}");
                    else
                        Console.Write($"{numTasks[indexTasks[j]]}, ");


                }
                Console.WriteLine();
            }
        }

        static int ChoiseNum()
        {
            bool isAdd = false;
            int num = 0;
            Random rnd = new Random();
            do
            {
                num = rnd.Next(0, numTasks.Count);
                isAdd = CheckAvailability(num);
            } while (!isAdd);

            return num;
        }

        static bool CheckAvailability(int index)
        {
            bool result = true;
            for(int i = 0; i < indexTasks.Length; i++)
            {
                if(index == indexTasks[i])
                {
                    result = false;
                    break;
                }
            }

            return result;
        }
    }
}