AN INTRODUCTION TO THE .NET

WHAT IS .NET?
.NET is Microsoft’s new strategy for the development and deployment
of software. Depending on your interests and development background,
you may already have a number of preconceived notions regarding
.NET. As we will see throughout this CodeNote:
• .NET fundamentally changes the way applications execute under
the Windows Operating System.
• With .NET Microsoft is, in effect, abandoning its traditional
stance, one which favors compiled components, and is embracing
interpreted technology (similar, in many ways, to the Java
paradigm).
• .NET brings about significant changes to both C++ and Visual
Basic, and introduces a new language called C# (pronounced
“C sharp”).
• .NET is built from the ground up with the Internet in mind, embracing
open Internet standards such as XML and HTTP. XML
is also used throughout the framework as both a messaging instrument
and for configuration files.

These are all noteworthy features of .NET, or more accurately the .NET
Framework, which consists of the platform and tools needed to develop
and deploy .NET applications. The .NET Framework can be distilled
into the following three entities:

1. The Common Language Runtime (CLR), which is the executionenvironment for all programs in the .NET Framework. The CLR is similar to a Java Virtual Machine (VM) in that it interprets
byte code and executes it on the fly, while simultaneously
providing services such as garbage collection and exception
handling. Unlike a Java VM, which is limited to the Java language,
the CLR is accessible from any compiler that produces
Microsoft Intermediate Language (IL) code, which is similar to
Java byte code. Code that executes inside the CLR is referred to
as managed code. Code that executes outside its boundaries is
called unmanaged code.

2. The Runtime classes, which provide hundreds of prewritten services
that clients can use. The Runtime classes are the building
blocks for .NET applications. Many technologies you may have
used in the past (ADO, for example) are now accessed through
these Runtime classes, as are basic operations such as I/O. Traditionally,
every language had its own unique supporting libraries,
accessible only from that particular language. String
manipulation, for example, was afforded to VB programmers
via the Visual Basic runtime, whereas C++ programmers depended
on libraries such as STL for similar functionality. The
.NET Runtime classes remove this limitation by uniformly offering
services to any compiler that targets the CLR. Those familiar
with Java will find the Runtime classes analogous to the
Java Class Libraries.

3. Visual Studio.NET (VS.NET), which is Microsoft’s newest version
of Visual Studio. VS.NET includes VB.NET, “managed”
C++, and C#, all of which translate source code into IL code.
VB.NET and VC.NET are the new versions of Visual Basic and
Visual C++, respectively. C# is a new Microsoft language that at
first glance appears to be a hybrid of C++ and Java. .NET development
does not have to be limited to these languages, however.
Any component or program produced by an IL-aware
compiler can run within the .NET Framework. (As of this writing,
other companies have announced IL compilers for Perl,
Python, and COBOL.) VS.NET also comes with a fully Integrated
Development Environment (IDE), which we will examine
in Chapter 7. Note the VS.NET IDE now houses the
development environments for both Visual C++ and Visual Basic.