在C#中基類引用指向派生對象更好還是派生類自己的對象更好

Question

在下面的示例中，我創建了三個對象，我想知道三個對象之間有什么區別，它是如何工作的以及使用哪個對象，並且第三個對象中有錯誤，那么為什么它顯示錯誤？

class Base
{

}
class Derived : Base
{

}
class Main
{
    Base base = new Derived();
    Derived derived = new Derived();
    Derived derived_1 = new Base(); 
}

Answer 1

繼承是你在上面的代碼中所做的。

Base base = new Derived() :

基類類型的對象保存派生類的對象，其中當您調用派生類中覆蓋的方法時，它將調用派生類方法。 如果該方法未被覆蓋，它將調用基類方法

Derived derived = new Derived() :

派生類對象持有派生類型的對象，您在其中調用它的方法，它只會調用派生類型的方法。 它不會檢查任何重寫的方法。

Derived derived_1 = new Base() :

這不會編譯，因為子類不能保存基類的對象。

Answer 2

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 )

檢查此鏈接： https : //msdn.microsoft.com/en-us/library/ms173149.aspx