private void btnDel_Click(object sender, EventArgs e)
{
DialogResult question = MessageBox.Show("Are you sure?", "", MessageBoxButtons.YesNo);
if (question == DialogResult.Yes)
{
//========================= Book-un silinmesi ====================================
// downcast edirik ve BookComboBox secilmish book ID nomresini bookId-ye veririk
string bookId = ((BookComboBox)cmbBookList.SelectedItem).Value;
// BookList-den secilmish book ID-ye gore tapib veririk Book tipinde bookForDelete-e
// bir nov apcast olunur ki Book-un icinden lazim olana catsin
Book bookForDelete = BookList.GetBookById(bookId);
// BookList-den Book classina girib Books siyahisindan
// ID-ci uyqun geleni silirik
BookList.Books.Remove(bookForDelete);
}
UpdateBookList();
}