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.

小心!注意类的可访问性。默认情况下，所有人都可以访问公共和受保护的类和方法。

此外，微软在显示访问修饰符(公共的，受保护的，等等。关键字)当Visual Studio中创建新类时。因此，请仔细考虑类的可访问性，因为它是通往实现内部的大门。

嗯…

静态意味着您可以在没有类实例的情况下访问该函数。

您可以直接从类定义中访问。

using System;

namespace ClassLibrary1
{
    public class SameAssemblyBaseClass
    {
        public string publicVariable = "public";
        protected string protectedVariable = "protected";
        protected internal string protected_InternalVariable = "protected internal";
        internal string internalVariable = "internal";
        private string privateVariable = "private";
        public void test()
        {
            // OK
            Console.WriteLine(privateVariable);

            // OK
            Console.WriteLine(publicVariable);

            // OK
            Console.WriteLine(protectedVariable);

            // OK
            Console.WriteLine(internalVariable);

            // OK
            Console.WriteLine(protected_InternalVariable);
        }
    }

    public class SameAssemblyDerivedClass : SameAssemblyBaseClass
    {
        public void test()
        {
            SameAssemblyDerivedClass p = new SameAssemblyDerivedClass();

            // NOT OK
            // Console.WriteLine(privateVariable);

            // OK
            Console.WriteLine(p.publicVariable);

            // OK
            Console.WriteLine(p.protectedVariable);

            // OK
            Console.WriteLine(p.internalVariable);

            // OK
            Console.WriteLine(p.protected_InternalVariable);
        }
    }

    public class SameAssemblyDifferentClass
    {
        public SameAssemblyDifferentClass()
        {
            SameAssemblyBaseClass p = new SameAssemblyBaseClass();

            // OK
            Console.WriteLine(p.publicVariable);

            // OK
            Console.WriteLine(p.internalVariable);

            // NOT OK
            // Console.WriteLine(privateVariable);

            // Error : 'ClassLibrary1.SameAssemblyBaseClass.protectedVariable' is inaccessible due to its protection level
            //Console.WriteLine(p.protectedVariable);

            // OK
            Console.WriteLine(p.protected_InternalVariable);
        }
    }
}

 using System;
        using ClassLibrary1;
        namespace ConsoleApplication4

{
    class DifferentAssemblyClass
    {
        public DifferentAssemblyClass()
        {
            SameAssemblyBaseClass p = new SameAssemblyBaseClass();

            // NOT OK
            // Console.WriteLine(p.privateVariable);

            // NOT OK
            // Console.WriteLine(p.internalVariable);

            // OK
            Console.WriteLine(p.publicVariable);

            // Error : 'ClassLibrary1.SameAssemblyBaseClass.protectedVariable' is inaccessible due to its protection level
            // Console.WriteLine(p.protectedVariable);

            // Error : 'ClassLibrary1.SameAssemblyBaseClass.protected_InternalVariable' is inaccessible due to its protection level
            // Console.WriteLine(p.protected_InternalVariable);
        }
    }

    class DifferentAssemblyDerivedClass : SameAssemblyBaseClass
    {
        static void Main(string[] args)
        {
            DifferentAssemblyDerivedClass p = new DifferentAssemblyDerivedClass();

            // NOT OK
            // Console.WriteLine(p.privateVariable);

            // NOT OK
            //Console.WriteLine(p.internalVariable);

            // OK
            Console.WriteLine(p.publicVariable);

            // OK
            Console.WriteLine(p.protectedVariable);

            // OK
            Console.WriteLine(p.protected_InternalVariable);

            SameAssemblyDerivedClass dd = new SameAssemblyDerivedClass();
            dd.test();
        }
    }
}

这些访问修饰符指定成员可见的位置。你应该读读这个。以IainMH给出的链接为起点。

静态成员是每个类一个，而不是每个实例一个。

我创建了另一种类型的可视化。也许这是更好的理解方式

https://github.com/TropinAlexey/C-sharp-Access-Modifiers