错误“存在显式转换(您是否缺少类型转换)"?在创建对象时出现: [英] Error "an explicit conversion exists (are you missing a cast )" comes when creating an object:

问题描述

我对学习OOP概念很感兴趣.在尝试使用继承的简单程序时.我已经注意到了这个错误.我不明白为什么会发生此错误?我在下面给出了简单的C#代码:

I am interested in learning OOPs concepts. While trying a simple program using Inheritance. I have noticed this error. I can't understand why this error occur? I have given that simple c# code below:

class Animal
{
    public void Body()
    {
        Console.WriteLine("Animal");
    }
}
class Dog : Animal
{
    public void Activity()
    {
        Console.WriteLine("Dog Activity");
    }
}

class Pomeranian : Dog
{
    static void Main(string[] args)
    {
        //Dog D = new Dog();
        Dog D = new Pomeranian();    -----> No error occur at this line
        Pomeranian P = new Dog();    -----> Error occur at this line
        D.Body();
        D.Activity();
        Console.ReadLine();
    }             
}

任何人都可以告诉我那里到底发生了什么...

Any one please tell me what is actually happening there...

推荐答案

您必须了解每只狗都是动物，但并非所有动物都是狗.

Program是一个可怕的名字，让我们摆脱它，使其成为Pomeranian:现在一切都会变得清晰起来.

Program is a terrible name, let's get rid of that and make it Pomeranian: now everthing will be clear.

Pomeranian P = new Dog();//This is not valid because not all dogs are Pomeranian.

但是您可以执行以下操作

but you can do the following

Dog d = new Pomeranian();//You know why this works :)

我希望这会有所帮助.

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