private void DataGridViewLectures_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.RowIndex < 0)
            {
                return;
            }
            var xt = (dgvLectures.Rows[e.RowIndex].DataBoundItem as TLecture);

            if (xt == null)
            {
                return;
            }

            if (Program.CurrentUser.IsStudent)
            {
                MessageBox.Show("Нямате права за редактиране на преподаватели!", "Предупреждение", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                return;
            }
            else if ((Program.CurrentUser.IsLecture && xt.FirstName.ToLower() == Program.CurrentUser.FirstName.ToLower() &&
                      xt.LastName.ToLower() == Program.CurrentUser.LastName.ToLower()) || Program.CurrentUser.IsAdmin)
            {
                FormAddRegistrationLecture lc = new FormAddRegistrationLecture();
                lc.lecture = xt;
                lc.ShowDialog();
            }
        }
        private void BtnLecturesAdd_Click(object sender, EventArgs e)
        {
            if (Program.CurrentUser.IsStudent)
            {
                MessageBox.Show("Нямате права за добавяне на преподаватели!", "Предупреждение", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                return;
            }
            FormAddRegistrationLecture lc = new FormAddRegistrationLecture();

            lc.ShowDialog();
        }