在下面的例子中，我创建了三个对象，我想知道这三个对象之间的区别是什么，它是如何工作的，使用哪个，第三个对象中有错误，为什么会显示错误？
class Base
{
}
class Derived : Base
{
}
class Main
{
Base base = new Derived();
Derived derived = new Derived();
Derived derived_1 = new Base();
}
Base base = new Derived();//Here you are referencing the derived object with base reference type, so only base members will be accessed using the base reference
Derived derived = new Derived();//Here you can access members in base and derived
Derived derived_1 = new Base();//This is a syntax error because you are using a derived reference for the base object(you are referencing a general object with a specific reference you need conversion here )
检查此链接：https://msdn.microsoft.com/en-us/library/ms173149.aspx
继承就是您在上面代码中所做的。
Base base = new Derived() :
基类类型的对象持有派生类的对象，当您在其中调用在派生类中重写的方法时，它将调用派生类方法。如果该方法未被重写，它将调用基类方法
Derived derived = new Derived() :
派生类对象包含派生类型的对象，您在其中调用它的方法，它将简单地调用派生类型的方法。它不会检查任何重写的方法。
Derived derived_1 = new Base() :
这将不会编译，因为子类不能容纳基类的对象。