What Is .NET ?

What Is .NET
Or, How I Learned to Stop Worrying and Love the Runtime
by James Avery, author of Visual Studio Hacks


.NET
The .NET Framework is Microsoft's application development platform
that enables developers to easily create Windows applications, web
applications, and web services using a myriad of different programming
languages, and without having to worry about low-level details like
memory management and processor-specific instructions.
In This Article:
The Runtime
Alternative CLR Implementations
The Library
The Tools
The Future
.NET is probably one of the more muddled and mismanaged brands in the
history of Microsoft. If you go to microsoft.com it will tell you that
".NET is the Microsoft Web services strategy to connect information,
people, systems, and devices through software," but this isn't what
most people are thinking of when they say, ".NET." What is commonly
referred to as .NET is programming with the .NET Framework. This is
what I am going to cover in this article. If you are looking for
marketing speak then please refer to www.microsoft.com/net.

The Runtime
At the heart of .NET is the Common Language Runtime, commonly referred
to as the CLR. The CLR is made up of a number of different parts,
which I will be covering here piece by piece (if you didn't want a
technical article then you should've followed the marketing link).

Language Independence
One of the most important facets of the .NET Framework is language
independence. You can write .NET applications using any number of
different programming languages. The most popular languages tend to be
C# and VB.NET, but many other languages now have .NET versions
including Python, COBOL, and more. You can see a list of many of the
languages you can use with .NET over at
dotnetpowered.com/languages.aspx.

Language independence is attained through the use of an intermediate
language (IL). What this means is that instead of code being compiled
in actual machine code (code that the CPU would run), it is instead
compiled into a high-level generic language. This means that whatever
language you write your code in, when you compile it with .NET it will
become IL. Since all languages eventually get translated into the
intermediate language, the runtime only has to worry about
understanding and working with the intermediate language instead of
the plethora of languages that you could actually use to write code.

Just-in-Time Compilation
If your mantra is, "Why do something now you can put off till
tomorrow?" then you have something in common with the CLR. When you
compile your code and it is translated to the intermediate language it
is then simply stored in an assembly. When that assembly is used the
CLR picks up that code and compiles it on-the-fly for the specific
machine that is running the code. This means the runtime could compile
the code differently based on what CPU or operating system the
application is being run on. However, at this point the CLR doesn't
compile everything in the assembly; it only compiles the individual
method that is being invoked. This kind of on-the-fly compilation,
referred to as jitting, only happens once per method call. The next
time a method is called, no compilation occurs because the CLR has
already compiled that code.

Memory Management
Related Reading


Visual Studio Hacks
Tips & Tools for Turbocharging the IDE
By James Avery

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One of the constant assailants on productivity in unmanaged
programming platforms is manually managing memory. Having to deal with
memory management is also one of the largest sources for bugs and
security holes in many applications. .NET removes the hassle of
manually managing memory through the use of the aptly named garbage
collector. Instead of the developer needing to remove objects from
memory, the garbage collector looks at the current objects in memory
and then decides which ones aren't needed anymore. For some developers
this will be a tough pill to swallow; if you are used to managing
memory then turning it over to an automated process can be somewhat
troubling. This is when you have to take a step back, stop worrying,
and embrace the runtime. There are bigger problems to solve (namely
the business problems that are probably the real goal).

Alternative CLR Implementations
The .NET runtime is actually based on a standard developed by
Microsoft called the CLI or Common Language Infrastructure, portions
of which have been submitted to Ecma as an international standard.
Because the CLR is based on an open standard, there have been a number
of alternative CLR implementations, most notably Rotor and Mono. Rotor
was a project from Microsoft Research, is a version of the CLR that
will run on Mac OS, and is shared source. Mono is an independent open
source implementation of the CLR that runs on various Linux
distributions. While "Write once, run away" is not always realistic
with .NET, there are some options available when it comes to other
platforms. (Some code can be moved without issue, but most will
require some tweaking, as different implementation includes different
functionality.)

The Library
While the runtime is definitely the most important part of .NET, you
can't do too much with it by itself. This is where the Base Class
Library (or BCL) comes in. The BCL includes a lot of the plumbing of
.NET, including the system types, IO, and functions for working with
text. In addition to the BCL, there is the Framework Class Library
(FCL). The FCL is an extended library that makes working with the .NET
Framework practical and includes the following major pieces:


ADO.NET
Most current applications involve working with databases, normally
more than one. ADO.NET is the data access component of the .NET
Framework and includes built-in providers for SQL Server, ODBC, OLEDB,
as well as Oracle.

Windows Forms
Windows forms are the .NET Framework method for building desktop-based
applications. Windows Forms are simply a managed wrapper over the
native Windows API, this means that you can write code for one version
of Windows and it will run on other versions without issue all the way
back to Windows 98 SE.

Windows forms applications do require the .NET Framework to run, which
means that anyone who downloads your application, or any computer it
is installed on, will need to also have the .NET Framework. The
framework can be easily installed through Windows Update, and is
completely free, but the download size can be troublesome for people
with a slower connection.

ASP.NET
ASP.NET is the part of the .NET Framework dedicated to building web
applications. Using ASP.NET you can build everything from a small
starter website to enterprise-level web applications. ASP.NET allows
you to write web applications without the need for a scripting
language, everything can be written in your .NET language of choice.

Since ASP.NET applications are simply rendering HTML for the browser,
there is no requirement for the .NET Framework on the client. Chances
are you have used a number of sites that have been written in ASP.NET
and you might not even have known it.

Web Services
With ASP.NET Web Services Microsoft has created a number of
time-saving features to make it easy to quickly write and expose web
services from your application. Just like the rest of .NET, ASP.NET
Web Services can be written in any .NET language. Through the use of
the Web Services Extensions (free download from Microsoft), you can
also add support for the new and ever-growing list of WS-*
specifications to your ASP.NET Web Services.

The Tools
One of the benefits of the .NET Framework is the great tools that are
available to the .NET developer. Visual Studio has long been
considered one of the premier IDEs on the market and does a lot to
increase developer productivity when working with the framework. There
are also a large number of open source tools available for .NET,
including many that mimic the tools available on other platforms. Some
of these include nUnit for unit testing, nAnt for building projects,
nCover for testing code coverage, nHibernate for object persistence,
and much more.

The Future
This November, Microsoft will launch .NET 2.0, the first major
revision of the .NET Framework. With this revision .NET will grow to
include a large amount of new functionality, not just in ASP.NET,
Windows Forms and the base library, but also with the addition of
support for new language features like generics to the runtime.
Microsoft has shown its commitment to this platform and will continue
to build upon .NET for years to come. (There is already some public
information available on the next version of .NET, which is code-named
Orcas.)

Author's Note: Thanks to Dave Donaldson, Jayme Davis, and Jim Holmes
for reviewing and providing valuable feedback on this article.

James Avery has been programming with Microsoft technologies for the
last 7 years and has been working with .NET since the second beta
release.