CSharp - Type Creation Access Modifiers

Introduction

A type or type member may control its accessibility to other types and other assemblies using access modifiers.

The following table lists five access modifiers you can use.

Modifier	Description
public	Fully accessible. This is the implicit accessibility for members of an enum or interface.
internal	Accessible only within the containing assembly or friend assemblies. This is the default accessibility for non-nested types.
private	Accessible only within the containing type. This is the default accessibility for members of a class or struct.
protected	Accessible only within the containing type or subclasses.
protected internal	The union of protected and internal accessibility.

Examples

Class2 is accessible from outside its assembly; Class1 is not:

class Class1 {}                  // Class1 is internal (default)
public class Class2 {}

ClassB exposes field x to other types in the same assembly.

x from ClassA can only be access inside ClassA.

class ClassA { 
   int x;           // x is private (default)
} 
class ClassB { 
   internal int x; 
}

Functions within Subclass can call MyMethod but not Test:

class BaseClass
{
       void Test()          {}      // Test is private (default)
       protected void MyMethod() {}
}

class Subclass : BaseClass
{
       void Test1() { Test(); }      // Error - cannot access Test
       void Test2() { MyMethod(); }       // OK
}