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.NET Framework
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.
DOTNET 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
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.)
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