3.3. Overview of Class Members

Table 3-1 provides a summary of the types that comprise a .NET class. They can be classified broadly as members that hold data—constants, fields, and properties—and members that provide functionality—the constructor, method, and event. We'll look at each individually.

Table 3-1. Class Members

Member Type	Valid In	Description
Constant	Class, Structure	A symbol that represents an unchanging value. The compiler associates it with the class—not an instance of the class.
Field	Class, Structure	A variable that holds a data value. It may be read-only or read/write.
Property	Class, Structure	Provides access to a value in a class. It uses an accessor that specifies the code to be executed in order to read or write the value. The code to read or write to a property is implemented implicitly by .NET as two separate methods.
Constructor	Class, Structure	C# has three types of constructors: Instance. Initializes fields when an instance of a class is created. Private. Commonly used to prevent instances of a class from being created. Static. Initializes class before any instance is created.
Method	Class, Structure, Interface	A function associated with the class that defines an action or computation.
Events	Class, Structure, Interface	A way for a class or object to notify other classes or objects that its state has changed.
Types	Class, Structure, Interface	Classes, interfaces, structs, delegates.

Member Access Modifiers

The access modifiers used for a class declaration can also be applied to class members. They determine the classes and assemblies that have access to the class. Table 3-2 summarizes the scope of accessibility.

Table 3-2. Summary of Accessibility Provided by Access Modifiers

	Access Modifiers
Class can be accessed by classes in:	Public	protected	Internal	private
Another assembly	Yes	[*]	No	[*]
Same assembly	Yes	[*]	Yes	[*]
Containing class	Yes	Yes	Yes	Yes
Class derived from containing class	Yes	Yes	Yes	No

^[*] Not applicable