1. typeof 引數是一個型別名稱，比如你自己編寫的一個類
2. GetType()是類的方法，繼承自object，返回該例項的型別
3. is 用來檢測例項的相容性（是否可以相互轉換）

例：

class Animal { } 
class Dog : Animal { }

void PrintTypes(Animal a) { 
    Console.WriteLine(a.GetType() == typeof(Animal)); // false 
    Console.WriteLine(a is Animal);                   // true 
    Console.WriteLine(a.GetType() == typeof
 
(Dog));    // true
    Console.WriteLine(a is Dog);                      // true 
}

Dog spot = new Dog(); 
PrintTypes(spot);

對於泛型：typeof(T)

T總是表示式的型別，泛型方法基本上是一組具有適當型別的方法

例：

            Animal probably_a_dog = new Dog();
            Dog definitely_a_dog = new Dog();

            Foo(probably_a_dog); 
 
// this calls Foo<Animal> and returns "Animal"
            Foo<Animal>(probably_a_dog); // this is exactly the same as above
            Foo<Dog>(probably_a_dog); // !!! This will not compile. The parameter expects a Dog, you cannot pass in an Animal.

            Foo(definitely_a_dog); 
 
// this calls Foo<Dog> and returns "Dog"
            Foo<Dog>(definitely_a_dog); // this is exactly the same as above.
            Foo<Animal>(definitely_a_dog); // this calls Foo<Animal> and returns "Animal". 
            Foo((Animal)definitely_a_dog); // this does the same as above, returns "Animal"