C# 0 The Complete Reference

kevt.OnKeyPress( )

 when a key is pressed. This causes 

the registered event handlers to be notified. When the loop ends, the number of keypresses 

is displayed. Although quite simple, this example illustrates the essence of event handling. 

The same basic approach will be used for other event handling situations. Of course, in 

some cases, anonymous event handlers will not be appropriate and named methods will 

need to be employed.

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16

Namespaces, the 

Preprocessor, and Assemblies

T

his chapter discusses three C# features that give you greater control over the 

organization and accessibility of a program. These are namespaces, the preprocessor, 

and assemblies.

Namespaces

The namespace was mentioned briefly in Chapter 2 because it is a concept fundamental to 

C#. In fact, every C# program makes use of a namespace in one way or another. We didn’t 

need to examine namespaces in detail before now because C# automatically provides a 

default, global namespace for your program. Thus, the programs in earlier chapters simply 

used the global namespace. In the real world, however, many programs will need to create 

their own namespaces or interact with other namespaces. Here, they are examined in detail.

A

namespace

 defines a declarative region that provides a way to keep one set of names 

separate from another. In essence, names declared in one namespace will not conflict with 

the same names declared in another. The namespace used by the .NET Framework library 

(which is the C# library) is 

System

. This is why you have included

using System;

near the top of every program. As explained in Chapter 14, the I/O classes are defined 

within a namespace subordinate to