How to convert numeric elements to array in textBox?

Question

C++ / C#

Given 2 textboxes and a listbox where an array of numbers is displayed. In 2 textboxes, you need to enter numbers, in other words, numbers from which the number of positive and negative random numbers is converted. How can I code such a cumbersome thing, please tell me.

int a;
        int b;
        int N = a + b;
        int[] mas = new int[10];
        int[] mas2 = new int[10];

        Random rnd = new Random();
        private void button1_Click(object sender, EventArgs e)
        {
            a = Convert.ToInt32(textBox1.Text);
            b = Convert.ToInt32(textBox2.Text);
            for (int i = 0; i < N; i++)
            {
                mas[i] = rnd.Next(0, 11) ;
                listBox1.Items.Add(mas[i].ToString());

                mas2[i] = rnd.Next(0, -11);
                listBox1.Items.Add(mas[i].ToString());
            }
        }