有关C#中的新修饰符的帮助 [英] Help regarding new modifier in C#

问题描述

Hi,

public class ClassA
{
public   void MethodNew()
{
Console.WriteLine("In MethodNew of ClassA");
}

public virtual void MethodOverride()
{
Console.WriteLine("In MethodOverride of ClassA");
}
}

    public class ClassB : ClassA
    {
        public new void MethodNew()
        {
            Console.WriteLine("In MethodNew of ClassB");
        }

        public override void MethodOverride()
        {
            Console.WriteLine("In MethodOverride of ClassB");
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            ClassA a = new ClassB();
            a.MethodNew();
            a.MethodOverride();
        }
    }

在上面的示例中，尽管我在派生类中为Methodnew函数添加了不添加新关键字，但o/p始终在基类中调用方法...

那么在这里使用new的目的是什么?

In the above sample eventhough I append or not new keyword for Methodnew function in the derived class,the o/p is always calling method in base class...

So what is the purpose of using new here?

推荐答案

这是正确的行为，因为:

• 您正在使用多态性创建ClassB实例.
• 基类" MethodNew不是virtual.

That''s the correct behaviour, since:

• You''re using polymorphism to create ClassB instance.
• Base class'' MethodNew is NOT virtual.

我的问题是关于修饰符new的，就像在公共new void MethodNew()中一样，而不是用于初始化的运算符new.修饰符new是完全不同的东西，它用于隐藏成员时消除编译器警告.

请考虑以下内容:

I thing the question is about modifier new as in public new void MethodNew(), not operator new used for initialization. The modifier new is absolutely different thing, it''s used to dismiss compiler warning when hiding a member.

Consider the following:

class Base {
    protected void Visible() { }
} //class Base

class AccedentallyHiding : Base {
    //will shows warning: Visible() hides inherited member
    //Base.Visible(). Use the new keyword if hiding is intended
    protected void Visible() { }
} //class AccedentallyHiding

class IntentionallyHiding : Base {
    //no problem: keyword "new" shows intended hiding
    protected new void Visible() { }
} //class IntentionallyHiding

请参阅解释编译器行为的代码注释.

—SA

Please see code comments explaining compiler behavior.

—SA

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