Parallel for

    int[] nums = Enumerable.Range(0, 1000000).ToArray();
        int[] results = new int[nums.Length];
        Parallel.For(0, nums.Length, (i,loopsatate) =>
            {
                if (i < 100)

                    results[i] = 2 * nums[i];

                else
                {
                    loopsatate.Stop();
                    return;
                }
            }
            );