Access Modifiers

Modifiers are C# keywords used to modify declarations of types and type members.
types - classes, structs, interfaces, enum
type members - field, properties, methods, indexers

Modifier	Type	Description
abstract	Classes Methods	Indicates that a class is just a base class. Indicates that a method must have a new implementation in a derived class In VB.Net this is MustInherit \| MustOverride
const	Constants	Indicates these values are known at compile time and do not change
extern	Methods	Indicates that a method is implemented externally
internal	Classes Methods Properties	Indicates the member can be accessed by any code in the same assembly but not from other assemblies. This is the default for classes and structures. A member of an internal class that has a public modifier is actually internal (check) In VB.Net this is Friend. In VB.Net this is the default for classes, structures, interfaces, delegates, enumerations and modules.
new		Replaces the member in the base class. When a member of a derived class has the same name as its base class then the derived class instance replaces that in the base class. This is the default for any members with the same name but using this modifier will remove the automatic warning. In VB.Net this is Shadows
override	Methods	Indicates that the method is a new implementation for a base class virtual member. In VB.Net this is Overrides
partial	Classes Methods	Allows you to split a class definition into separate source files.
public	Classes Methods Properties Constants	Indicates the member can be accessed by any code in the same assembly or another assembly that references it. There are no restrictions. It is completely visible. Can be called from outside that class and from other assemblies. This is the default for namespaces, interfaces and enumerations. In VB.Net this is the default for methods.
private	Classes Methods Properties Constants	Indicates the member can only be accessed by code inside the class or struct. It is good practice to keep all fields private. This is the default for (nested) classes and structures.
protected	Methods	Indicates the member can be accessed only by code inside the class or structure OR in a class derived from that class.
protected internal		Indicates the method can be accessed by any code in the same assembly OR from within a derived class in another assembly. Using 'internal protected' will also work but is never used.
readonly	Constants	Can only be assigned a value in the declaration or in the constructor
sealed	Classes	Indicates that a class cannot be inherited. Indicates that a method cannot have a new implementation in a derived class (cannot be overridden) In VB.Net this is NotInheritable \| NotOverridable
static	Constants Fields Methods	Indicates that a member belongs to the type itself and does not require an instance of the object A class can provide a container for methods that do not have to modify any internal instance fields or properties. A static class is the same as having only static members and a private constructor A static class is also a sealed class. In VB.Net this is Shared
unsafe	Methods Properties	Required for any operation involving pointers
virtual	Methods Properties	A method may be overridden. A class can be overridden in a derived class. A method can be modified by the operating system, the hardware or a concurrently executing thread. In VB.Net this is Overrideable
volatile	Fields	Can be modified by something else, eg hardware or a concurrent thread