类型检查：typeof，GetType还是？

类型检查：typeof，GetType还是？

都是不同的。

• typeof

  采用类型名称（您在编译时指定）。

• GetType

  获取实例的运行时类型。

• is

  如果实例在继承树中，则返回true。

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);

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那

typeof(T)

呢 在编译时也解决了吗？

是。T始终是表达式的类型。请记住，泛型方法基本上是一堆具有适当类型的方法。例：

string Foo<T>(T parameter) { return typeof(T).Name; }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 aboveFoo<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"