C#多态 [英] C# Polymorphism

问题描述

运行时多态性和编译时多态性有什么区别?另外，早装订和晚装订有什么区别?实例将不胜感激.

What's the difference between run-time polymorphism and compile-time polymorphism? Also, what's the difference between early binding and late binding? Examples would be highly appreciated.

推荐答案

编译时多态性

方法重载就是一个很好的例子.您可以使用名称相同但签名不同的两个方法.编译器将在编译时选择要使用的正确版本.

Method overloading is a great example. You can have two methods with the same name but with different signatures. The compiler will choose the correct version to use at compile time.

运行时多态性

从子类的父类重写虚拟方法是一个很好的例子.另一个是从接口实现方法的类.这样，您就可以在使用子级指定的实现时，在代码中使用更通用的类型.给定以下类定义:

Overriding a virtual method from a parent class in a child class is a good example. Another is a class implementing methods from an Interface. This allows you to use the more generic type in code while using the implementation specified by the child. Given the following class definitions:

public class Parent
{
    public virtual void SayHello() { Console.WriteLine("Hello World!"); }
}

public class Child : Parent
{
    public override void SayHello() { Console.WriteLine("Goodbye World!"); }
}

以下代码将输出"Goodbye World！":

The following code will output "Goodbye World!":

Parent instance = new Child();
instance.SayHello();

早期绑定

在编译时指定类型:

SqlConnection conn = new SqlConnection();

后期绑定

类型在运行时确定:

object conn = Activator.CreateInstance("System.Data.SqlClient.SqlConnection");

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