public static void CastingDemo()
{
// putting a more-specifically-typed value in a more generally-typed container
IOutputter o = new Outputter(); // upcasting
HelperMethod(new Outputter()); // upcasting
// upcasting is safe, implicit (you don't have to cast with () )
Outputter o2 = (Outputter)o; // downcasting
// because the compiler can't know for sure that this will work,
// C# says, you have to declare your certainty that it should work with () operater.
// if you were wrong, it will throw an exception at runtime.
// downcasting is explicit
// other kinds of casting, like numeric conversions.
double x = 5.5;
int a = (int)x; // int can't represent every possible double, so data could be lost if we want this to happen
// (it doesn't round-to-nearest-integer, it truncates, discards the decimal places)
double y = a; // double can represent every possible int, so this is safe, so it's an implicit conversion
// boxing and unboxing
// value types behave in one way when you pass them to a new variable (copy the value)
// reference types behave in a different way (copy the reference)
int x2 = 3;
object o3 = x2; // the value is wrapped in a object on the heap, so that o3 can have the reference-type semantics we expect.
// that's called boxing.
int y2 = (int)o3; // unboxing the value.
// C# supports operator overloading
// you can make your class work with +, ==, [], etc
// you can even define your own custom implicit casts and explicit casts.
}
public static void HelperMethod(IOutputter o)
{
Outputter o2 = (Outputter)o; // downcasting
}