c# 反射如何成为运行时事件？

Question

Every definition says C# reflections is used to determine type of object in runtime. Can the type of an object change in runtime? Can anybody please provide me an example.

Answer 1

Of course an entity can change its runtime type during runtime. It just can't change its compile type. This is because c# is a type safe language (once a given type, always a given type).

Suppose you have 3 classes - one an abstract class say Animal and two classes that derive from it, say Cat and Dog . Then

Animal animal = new Dog(); //compile time type is Animal runtime type is Dog
Console.WriteLine(animal.GetType().Name); // Dog
...
animal = new Cat(); // compile time type is still Animal (c# is Type safe)
// but runtime type just changed to Cat;
Console.WriteLine(animal.GetType().Name); // Cat

Notice that all the while you are programming your Animal animal will not be "just an object". Being of (compile) type Animal bears great tiding - bool IsAlive property, Breath() method, and more. But when you write your code (ie compile time) your "animal" instance won't have a Tail (because not every animal has a tail). You can only access (with intellisense for example) things that you are sure it has (only Animal things). That's still saying a lot, but not as much as it's concrete subclasses. It's a very general thing, and that's a good thing.