students

 public void Selection()
        {
            flag = true;
            position = 0;
            textBox1.Enabled = true;
            textBox2.Enabled = true;
            textBox3.Enabled = true;
            Findindex();
            if (textBox4.Text.Length != 0 && t.Item1 != -1)
            {
                position = t.Item1;

                Output();
                IsMaster();
                CheckButton();
                CheckMenu();
            }
            else if ((textBox4.Text.Length != 0 && t.Item1 == -1))
                {
                    position=-1;

                    textBox1.Clear();
                    textBox2.Clear();
                    textBox3.Clear();
                    textBox5.Clear();
                    textBox1.Enabled = false;
                    textBox2.Enabled = false;
                    textBox3.Enabled = false;
                    textBox5.Enabled = false;

                }

                else
                {
                    position = 0;
                flag = false;
                if (list.Count() != 0)
                {
                    Output();
                    IsMaster();
                }
                else {
                    textBox1.Enabled = false;
                    textBox2.Enabled = false;
                    textBox3.Enabled = false;
                }
                    CheckButton();
                    CheckMenu();
                }


        }





private void удалитьToolStripMenuItem_Click(object sender, EventArgs e)
        {

           /* if (flag && position <= t.Item2 && position > t.Item1)
            {
                int it1 = t.Item1;
                int it2 = t.Item2-1;
                t = (it1, it2);
            }
            else if (flag && position < t.Item2 && position <= t.Item1)
            {
                int it1 = t.Item1+1;
                int it2 = t.Item2-1;
                t = (it1, it2);
            }*/
            list.RemoveAt(position);
            if (flag && position < t.Item2 && position > t.Item1)
            {
                int it1 = t.Item1;
                int it2 = t.Item2 - 1;
                t = (it1, it2);
            }
            else if (position == list.Count() || (position == t.Item2))
            {
                if (flag)
                {
                    Findindex();
                    position = t.Item2;
                }
                else position--;
            }
            else if (flag && position == t.Item1)
            {
                Findindex();
                position = t.Item1;
            }
             if (list.Count == 0 || (t.Item1 == -1 && flag))
            {

                textBox1.Clear();
                textBox2.Clear();
                textBox3.Clear();
                textBox5.Clear();
                textBox1.Enabled = false;
                textBox2.Enabled = false;
                textBox3.Enabled = false;
                textBox5.Enabled = false;
                button3.Visible = false;

                return;
            }


            Output();
            IsMaster();
            CheckButton();
            CheckMenu();


        }