接口和类之间的差异 [英] Difference Between Interface and Class

问题描述

由于标题状态我想知道使用类之间的区别如下

As the title states i want to know the difference between using the class like this

public class Account
{
    public string Username { get; set; }
    public string Password { get; set; }
}

并使用此接口

public class Account : IAccount
{
    public string Username { get; set; }
    public string Password { get; set; }
}

public interface IAccount
{
    string Username { get; set; }
    string Password { get; set; }
}

我真的很困惑，因为我发现接口是无用的，因为我可以做

I am really confused as i find interface is useless as all i can do with it can be done only using Class, Hence, i need someone to clarify things for me.

推荐答案

接口是一个 contract ：它指定实现接口必须具有的类的成员（方法和属性）。但是因为它只是一个合同，它没有任何成员的实现。类可以实现零个，一个或多个接口。

An interface is a contract: it specifies what members (methods and properties) a class implementing the interface must have. But because it is only a contract, it has no implementations for any of its members. A class can implement zero, one or multiple interfaces.

相反，类是一个... well ... （如分类法）。例如， Animal 是一类生物，长颈鹿是一类动物。继承表达这种关系：当时， c是 Giraffe 继承自 Animal 。它可以做任何动物可以做的，和更多。它可以为其成员提供实现，在.NET中，一个类将继承自另外一个类（除非另有说明，否则 Object ）。

In contrast: a class is a... well... class of objects (like in taxonomy). For example, an Animal is a class of living things, and a Giraffe is a class of animals. Inheritance expresses this relationship: an Giraffe is an Animal when Giraffe inherits from Animal. It can do anything an animal can do, and more. It can provide implementations for its members, and in .NET a class will inherit from exactly one other class (which is Object unless specified otherwise).

所以，如果你想表达你的类遵守一个或多个合同：使用 interfaces 。但是，您不能提供实现。如果你想表达你的类是某事，请扩展一个基类。在这种情况下，您可以提供一个实现，但只能扩展一个基类。

So, if you want to express that your class adheres to one or more contracts: use interfaces. However, you cannot provide an implementation. If you want to express that your class is something, extend a base class. In that case you can provide an implementation, but you can extend only one base class.

一个具体的例子：

链表，数组列表，堆栈和字典有一些共同点：它们代表一组元素。但是它们的实现是完全不同的。他们唯一共同的是他们坚持的合同： ICollection 。这意味着你的类可以请求一个集合，任何集合：任何实现 ICollection ，无论其实现。

A linked list, an array list, a stack and a dictionary have something in common: they represent a collection of elements. But their implementations are completely different. The only thing they have in common is the contract they adhere to: ICollection. This means your classes can ask for a collection, any collection: anything that implements ICollection, regardless of its implementation.

另一方面：汽车，摩托车和卡车也有一些共同点：它们是轮式车辆。但他们有更多的共同点：他们都有一个电机，他们都旋转他们的轮胎向前。基本上，它们是 Vehicle 类的对象的成员，并且可以共享（部分）它们的实现。但是，卡车可能是车辆 和 CargoCarrier ，你不能在C＃中表达。

On the other hand: a car, a motorcycle and a truck also have something in common: they are wheeled vehicles. But they have more in common than that: they all have a motor, they all spin their tires to go forward. Essentially, they are members of the Vehicle class of objects, and can share (part of) their implementation. However, while a Truck may be a Vehicle and a CargoCarrier, you cannot express this in C#.

这篇关于接口和类之间的差异的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！