private void BtnAddUser_Click(object sender, EventArgs e)
        {
            if (!string.IsNullOrEmpty(TxtFirstName.Text) && !string.IsNullOrEmpty(TxtLastName.Text) && !string.IsNullOrEmpty(TxtPassword.Text) && (dateEnrollmentDate.Checked || dateHireDate.Checked) && comboBoxDisc.Text != null)
            {
                using (var db = new SchoolEntities())
                {
                    DateTime?dt         = null;
                    var      hireDate   = (dateHireDate.Enabled == true) ? dateHireDate.Value : dt;
                    var      enrollDate = (dateEnrollmentDate.Enabled == true) ? dateEnrollmentDate.Value : dt;

                    var person = new Person()
                    {
                        LastName = TxtLastName.Text, FirstName = TxtFirstName.Text, HireDate = hireDate, EnrollmentDate = enrollDate, Discriminator = comboBoxDisc.SelectedItem.ToString(), Password = TxtPassword.Text
                    };

                    db.Person.Add(person);
                    db.SaveChanges();

                    dataGridView1.DataSource = db.Person.ToList();
                    dataGridView1.Rows[dataGridView1.Rows.Count - 1].Selected = true;
                    dataGridView1.FirstDisplayedCell = dataGridView1.Rows[dataGridView1.Rows.Count - 1].Cells[0];
                }

                TxtFirstName.ResetText();
                TxtLastName.ResetText();
                TxtPassword.ResetText();
                dateHireDate.ResetText();
                dateEnrollmentDate.ResetText();
                comboBoxDisc.SelectedItem = null;
            }
            else
            {
                MessageBox.Show("You havent entered every needed information.", "Information", MessageBoxButtons.OK, MessageBoxIcon.Warning);
            }
        }