static void Main(string[] args)
{
Overrider overrider = new Overrider();
BaseClass b1 = overrider;
overrider.Foo(); //Overrider.Foo //重写会改变我的这个方法或属性
b1.Foo(); //Overrider.Foo //重写会改变我的这个方法或属性
Hider hider = new Hider();
BaseClass b2 = hider;
hider.Foo(); //Hider.Foo //new关键字重写会改变我的这个方法或属性
b2.Foo(); //BaseClass.Foo //new关键字但不会改变我原本的这个方法或属性
}
public static void Main(string[] args)
{
Overrider over = new Overrider();
BaseClass b1 = over;
over.Foo();
b1.Foo();
Hider h = new Hider();
BaseClass b2 = h;
h.Foo();
b2.Foo();
}
static void tstHiding()
{
//The differences in behavior between Overrider and Hider are demonstrated in the following code:
Overrider over = new Overrider();
BaseClass b1 = over;
over.Foo(); // Overrider.Foo
b1.Foo(); // Overrider.Foo
Hider h = new Hider();
BaseClass b2 = h;
h.Foo(); // Hider.Foo
b2.Foo(); // BaseClass.Foo
}
static void Main(string[] args)
{
var over = new Overrider();
BaseClass b1 = over;
over.Foo();
b1.Foo();
var h = new Hider();
BaseClass b2 = h;
h.Foo();
b2.Foo();
Console.ReadKey();
}
public static void Main()
{
Overrider over = new Overrider();
BaseClass b1 = over;
over.Foo();
b1.Foo();
Console.WriteLine();
Hider h = new Hider();
BaseClass b2 = h;
h.Foo();
b2.Foo();
}
static void tstHiding() {
//The differences in behavior between Overrider and Hider are demonstrated in the following code:
Overrider over = new Overrider();
BaseClass b1 = over;
over.Foo(); // Overrider.Foo
b1.Foo(); // Overrider.Foo
Hider h = new Hider();
BaseClass b2 = h;
h.Foo(); // Hider.Foo
b2.Foo(); // BaseClass.Foo
}
static void Main(string[] args)
{
Stock msft = new Stock
{
Name = "MSFT",
SharesOwned = 1000L
};
Console.WriteLine(msft.Name);
Console.WriteLine(msft.SharesOwned);
Console.WriteLine(msft);
House mansion = new House
{
Name = "Mansion",
Mortgage = 250000M
};
Console.WriteLine(mansion);
Console.WriteLine(mansion.Name);
Console.WriteLine(mansion.Mortgage);
Console.WriteLine(mansion.Liability);
// polymorphism
Display(msft);
Display(mansion);
// Upcast : implicitly upcast to a base class reference
Asset a = msft;
// True :
Console.WriteLine(a == msft);
// OK :
Console.WriteLine(a.Name);
// Error: SharesOwned undefined
// Console.WriteLine(a.SharesOwned);
// Downcast : explicitly downcast to a subclass reference
Stock s = (Stock)a;
// <No error>
Console.WriteLine(s.SharesOwned);
// True :
Console.WriteLine(s == a);
// True :
Console.WriteLine(s == msft);
// as operator performs a downcast that evaluates to null (rather than throwing
// an exception) if the downcast fails
Asset asserNull = new Asset();
Stock t = asserNull as Stock;
// t is null; no exception thrown
Console.WriteLine(t?.SharesOwned);
// new versus override
Overrider over = new Overrider();
BaseClass b1 = over;
over.Foo();
// Overrider.Foo
b1.Foo();
// Overrider.Foo
Hider h = new Hider();
BaseClass b2 = h;
h.Foo();
// Hider.Foo
b2.Foo();
// BaseClass.Foo
// Boxing : convert a value-type instance to a reference-type instance
int x = 9;
// box the int into an object
object obj = x;
// Unboxing : cast the object back to the original value type
// Unboxing : requires an explicit cast
int y = (int)obj;
x = 5;
// changing the value of x doesn’t change its previously boxed copy
Console.WriteLine(obj); // 9
}