在C#中，有如下几种修饰符，分别是public,protected,internal,private。先来看一下C# 4th Edition中的说明：
public
No restrictions. Members marked public are visible to any method of any class.
private
The members in class A that are marked private are accessible only to methods of class A.
protected
The members in class A that are marked protected are accessible to methods of class A and also to methods of classes derived from class A.
internal
The members in class A that are marked internal are accessible to methods of any class in A's assembly.
protected internal
The members in class A that are marked protected internal are accessible to methods of class A, to methods of classes derived from class A, and also to any class in A's assembly. This is effectively protected OR internal. (There is no concept of protected AND internal.)
下面是C#中修饰符的具体意义：
| 修饰符 | 应用于 | 说明 |
| public | 所有的类型或成员 | 任何代码均可以访问该成员 |
| protected | 类型和内嵌类型（即在一个类中定义的类）的所有成员 | 只有派生的类型能访问该成员 |
| internal | 类型和内嵌类型的所有成员 | 只能在包含它的程序集中访问该成员 |
| private | 所有的类型或成员 | 只能在它所属的类型中访问该成员 |
| protected internal | 类型和内嵌类型的所有成员 | 能在包含它的程序集或派生类型中访问该成员 |
| new | 函数成员 | 成员用相同的签名隐藏继承的成员 |
| static | 所有的成员 | 成员不在类的具体实例中执行 |
| virtual | 仅函数成员 | 成员可以由派生类重写 |
| abstract | 类和函数成员 | 抽象成员定义了成员的签名，但没有提供实现代码 |
| override | 仅函数成员 | 成员重写了继承的虚拟或抽象成员 |
| sealed | 类 | 成员重写了继承的虚拟成员，但继承该类的任何类都不能重写该成员。必须与override一起使用 |
| extern | 仅静态[DllImport]方法 | 成员在外部用另一种语言实现 |
以上摘自 浪漫如枫
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