大学期间我一直在使用public,想知道public, private和protected之间的区别吗?
还有,相对于什么都没有,静态有什么作用呢?
大学期间我一直在使用public,想知道public, private和protected之间的区别吗?
还有,相对于什么都没有,静态有什么作用呢?
当前回答
图形概述(简要总结)
实际上,情况要比这复杂一些。 现在(从c# 7.2开始),也有private protected,派生类是否在同一个程序集中也很重要。
因此,需要扩展概述:
请参阅有关此主题的c# -dotnet-docs。
因为静态类是密封的,所以它们不能被继承(除非是从Object继承),所以关键字protected在静态类上是无效的。
对于默认情况,如果你在前面不放访问修饰符,请参见这里: c#类和成员(字段,方法等)的默认可见性?
Non-nested
enum public
non-nested classes / structs internal
interfaces internal
delegates in namespace internal
class/struct member(s) private
delegates nested in class/struct private
嵌套:
nested enum public
nested interface public
nested class private
nested struct private
此外,还有seal -关键字,它使类不可继承。 同样,在VB中。NET,关键字有时是不同的,所以这里有一个小抄:
其他回答
Hmm.
参见这里:访问修饰符。
简而言之:
Public使方法或类型从其他类型/类中完全可见。
Private只允许包含私有方法/变量的类型访问私有方法/变量(注意,嵌套类也可以访问包含类的私有方法/变量)。
Protected与private类似,只是派生类也可以访问Protected方法。
“Nothing”是VB。NET等价于null。虽然如果你提到的“nothing”意味着“没有访问修饰符”,那么这要视情况而定,尽管一个非常粗略的经验法则(当然在c#中)是,如果你没有显式地指定访问修饰符,方法/变量声明通常会受到尽可能多的限制。 即。
public class MyClass
{
string s = "";
}
实际上等同于:
public class MyClass
{
private string s = "";
}
当没有显式指定访问修饰符时,链接的MSDN文章将提供完整的描述。
Private状态表示变量只能被同一类的对象访问。受保护状态将这种访问权限扩展到该类的后代。
“从上表中我们可以看到隐私和受保护之间的区别……我认为两者是一样的....那么这两个单独的命令有什么用呢?
查看MSDN链接了解更多信息
图形概述(简要总结)
实际上,情况要比这复杂一些。 现在(从c# 7.2开始),也有private protected,派生类是否在同一个程序集中也很重要。
因此,需要扩展概述:
请参阅有关此主题的c# -dotnet-docs。
因为静态类是密封的,所以它们不能被继承(除非是从Object继承),所以关键字protected在静态类上是无效的。
对于默认情况,如果你在前面不放访问修饰符,请参见这里: c#类和成员(字段,方法等)的默认可见性?
Non-nested
enum public
non-nested classes / structs internal
interfaces internal
delegates in namespace internal
class/struct member(s) private
delegates nested in class/struct private
嵌套:
nested enum public
nested interface public
nested class private
nested struct private
此外,还有seal -关键字,它使类不可继承。 同样,在VB中。NET,关键字有时是不同的,所以这里有一个小抄:
public means that it can be accessed by any class in any assembly, which includes the class itself. protected internal means it can be accessed by the class itself (in the class definition), and it can be accessed by any class in the current assembly, but outside of the assembly it can only be accessed by a class that inherits the class, or by the class itself (if it is a partial class) – basically it means internal inside the assembly and protected outside of the assembly. protected means it can only be accessed by the class itself, or accessed by a class that inherits it and that class can be in any assembly internal means it can be accessed by the class itself or by any class in the assembly but can't be accessed at all outside of the assembly unless by the class itself (i.e. it is a partial class) private protected means it can only be accessed by the class itself, or it can be accessed by a class that inherits it and only if that class is in the current assembly. Outside of the assembly, it can only be accessed by the class itself (i.e. it is a partial class) – basically combines internal and protected, or another way of putting it is it's private outside of the assembly and protected inside the assembly. private means that it can only be accessed by the class itself no access modifier: The default access for everything in C# is "the most restricted access you could declare for that member"., which is private for a member / method / nested class in a class and internal for a non-nested class.
In the above text 'accessed' means accessed via an object of the class type, which within a method of the class itself will be the implicit this object, or perhaps the method instantiates an explicit object of the current class type and accesses it through that object. Both are considered to be being accessed by the class itself and therefore the access rules are the same. This also applies to an access being performed from a static method, or when it is a static member / method being accessed, except the access is performed using the class scope and not and object. A member / method of a static class needs to be explicitly made static or it won't compile.
没有嵌套的类可以是公共的,也可以是内部的,默认情况下是内部的。嵌套的类可以是任何访问类型,如果父类是静态的,它就不需要是静态的,它的成员也不需要是静态的。内部类意味着只能实例化它或从当前程序集访问它的静态成员。
您可以在内部或私有嵌套类中拥有公共成员/方法/嵌套类——只有访问说明符(在正在进行的访问的完全限定名称中)低于当前正在进行的访问所需的级别才能阻止访问。
Inheritance in C# is always public unlike C++, which can privately or protectedly inherit, which then changes the access of all classes that then inherit from the class that is inheriting from this class, as well as the access via object / via class scope of type of the class that inheriting privately / protectedly from the class and the class that is inheriting from the class that is inheriting privately / protectedly form the class, and so on. The access is changed such that all access modifiers less restrictive than private or protected are made private and protected respectively.
c#中所有访问修饰符的描述