Datasheet

❑ File system and registry access (see Chapter 24, “Manipulating Files and the Registry”)
❑ Networking and Web browsing (see Chapter 35, “Accessing the Internet”)
❑ .NET attributes and reflection (see Chapter 12, “Reflection”)
❑ Access to aspects of the Windows OS (environment variables and so on; see Chapter 19, “.NET
Security”)
❑ COM interoperability (see Chapters 38, “Enterprise Services” and 23, “COM Interoperability”)
Incidentally, according to Microsoft sources, a large proportion of the .NET base classes have actually
been written in C#!
Namespaces
Namespaces are the way that .NET avoids name clashes between classes. They are designed to avoid
the situation in which you define a class to represent a customer, name your class
Customer, and then
someone else does the same thing (a likely scenario — the proportion of businesses that have customers
seems to be quite high).
A namespace is no more than a grouping of data types, but it has the effect that the names of all data
types within a namespace are automatically prefixed with the name of the namespace. It is also possible
to nest namespaces within each other. For example, most of the general-purpose .NET base classes are in a
namespace called
System. The base class Array is in this namespace, so its full name is System.Array.
.NET requires all types to be defined in a namespace; for example, you could place your
Customer class
in a namespace called YourCompanyName. This class would have the full name YourCompanyName.Customer.
If a namespace is not explicitly supplied, the type will be added to a nameless global namespace.
Microsoft recommends that for most purposes you supply at least two nested namespace names: the
first one refers to the name of your company, and the second one refers to the name of the technology or
software package that the class is a member of, such as
YourCompanyName.SalesServices.Customer.
This protects, in most situations, the classes in your application from possible name clashes with classes
written by other organizations.
Chapter 2, “C# Basics,” looks more closely at namespaces.
Creating .NET Applications Using C#
C# can also be used to create console applications: text-only applications that run in a DOS window.
You’ll probably use console applications when unit testing class libraries, and for creating Unix or Linux
daemon processes. However, more often you’ll use C# to create applications that use many of the tech-
nologies associated with .NET. This section gives you an overview of the different types of applications
that you can write in C#.
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