C# 轉(zhuǎn)換

Product myProduct = new Product(); 
Item a = myProduct; // Upcast 

Console.WriteLine (a == myProduct); // True 

Console.WriteLine (a.Name); // OK 
Console.WriteLine (a.InStoreCount); // Error: InStoreCount undefined 

Product myProduct = new Product(); 
Item a = myProduct; // Upcast 

Product s = (Product)a; // Downcast 

Console.WriteLine (s.InStoreCount); 
Console.WriteLine (s == a);         // True 
Console.WriteLine (s == myProduct); // True 

DiscountProduct h = new DiscountProduct(); 
Item a = h; // Upcast always succeeds 
Product s = (Product)a; // Downcast fails: a is not a Product 

Item a = new Item(); 
Product s = a as Product; // s is null; no exception thrown 

if (s != null) {
   Console.WriteLine (s.InStoreCount); 
}