What is .Net


I have some .Net related content that I plan to post and thought that I would revisit this question.

It’s a question I find interesting in that the answer has changed slightly over the year. In the earliest years it was a branding for technologies that were not necessarily related to each other; Windows .NET Server and Windows .NET Messenger are two products that had the branding at one point. But let’s not walk down memory lane and jump straight into the answer.

.NET is still a branding but the technologies with the branding are related to each other. Microsoft uses the branding on their Common Language Runtime (CLR) products. That answer only has kicked the can down the road. What is the CLR?

The CLR is a virtual machine component. Executables targeting the CLR don’t necessarily contain any code that is native to the processor on which they are running (though it may contain native code, but let’s ignore that for a moment). CLR binaries can be distributed with no processor dependent executable code within them. At runtime when the code is being executed it is converted to machine code as needed. Because of this the same program can be run on machines that have different processor architectures. The computer on which a program is running needs to have the runtime that is specific to it’s architecture and operating system.

This system might sound familiar as modern Java does something similar. There was a time when Microsoft was invested in Java virtual machines and made the first Java runtime that compiled the Java binary to machine language. The entity that owned Java at the time (Sun) wasn’t happy about this and they took Microsoft to court for deviating from the standard of how Java virtual machines worked and for using the Internet as a method of distribution among other reasons. This disagreement might sound petty, and in part it was. But there were good reasons for their position that I’ll present in another post. But this interaction added weight to the argument that Microsoft should have their own virtual machine. They also made their own programming languages (C# and Visual Basic .NET) and a few CLRs for x86, x64, and for their mobile devices.

The CLR, also known as the .Net Framework has seen several updates over the years. Microsoft eventually decided to make the CLR open source. This contributed to another CLR implementation being created named Mono which allowed .Net Framework applications to run on Linux and Mac.

If you look up .Net now you’ll find a few .NET systems listed.

  • .Net Standard
  • .Net Core (2016)
  • .Net Framework (2002)
  • ASP.Net / ASP.Net Core

What are these?

.Net Standard is a specification of the set of APIs that are expected to be in all implementations of the .Net Framework. Think of this as analogous to an interface; .NET standard itself isn’t an implementation. If you make an application that sticks with these APIs then it will have a wide range of compatible targets.

For the .Net Framework only one version of the framework can be installed at a time. Microsoft generally kept backwards compatibility, but it wasn’t perfect. Since a system could only have one version of the Framework installed in corporations updating the Framework had to be a company level decision.

.Net Core was made to contain the most common features of the .Net Framework, but has a few new features installed. It was made with multiple operating systems in mind and multiple versions in mind.  A system can have multiple versions of .Net core installed and they can run side-by-side.  From hereon Microsoft will be putting efforts on improving .Net Core. The .Net Framework will continue to support the .Net Framework but don’t expect to see new features in it; the new features will be coming to .Net core. There are a lot of legacy functionality from the .Net Framework that did not get ported over to .Net core in the interest of performance and compatibility.

ASP (Active Server Pages) is the name for Microsoft’s Web development system. Some of the earlier versions used a language that was similar to Visual Basic (yuck). The first version of ASP that supported .NET was called ASP.NET. ASP.NET used the .Net runtime and the more recent version supports the .NET Core runtime.  Traditionally ASP pages were hosted within IIS (Internet Information Services), a Windows component for hosting web pages. Wit the modern versions while this is still an option ASP.NET pages can be hosted outside of IIS too.

If you are starting a new desktop .Net project and don’t know what version to use the safe choice will generally be .Net Core. In my opinion the best feature is its ability to run on multiple systems (Mac, Linux, Windows, and varios IoT devices including the Raspberry Pi).


Trying to learn C# and .Net Core? This is a book I would recomend.