//rent methood, throw mesaage every step that refort waht goes wrong
public bool RentBook(double money, TextBlock info, User user)
{
if (a.getCopies() <= 0)
{
throw new Exception("Not in stock!");
}
if (money == -1)
{
throw new Exception("Please enter money only!");
}
if (money < a.getDiscountPrice())
{
throw new Exception("Please enter enought money!");
}
// if this pass all the conditions he rentable
a.ReduceCopyAmount(); //remove copy from our list
info.Text = a.ToString(); //print the current detail's
user.RentItem(a); //add the item to list of the user
BookLib.ItemCollection.addToRental(user, a); //add to the Dictionary that manage the rentel
return(true);
}