private void dgvClassrooms_RowHeaderMouseDoubleClick(object sender, DataGridViewCellMouseEventArgs e)
        {
            int id = (int)dgvClassrooms.Rows[e.RowIndex].Cells[0].Value;

            selectedClassroom = dto.Get(id);

            txtClassroomName.Text = selectedClassroom.Name;
            numericCapacity.Value = selectedClassroom.Capacity;

            btnDelete.Visible = true;
            btnUpdate.Visible = true;
        }