What is “.NET Core”?

Question

Recently in an official .NET Framework Blog it was announced that .NET Core is going open source.

Ironically, the author mentions that what .NET Core is wil

Answer 1

.NET Core is an open source and cross platform version of .NET. Microsoft products, besides the great abilities that they have, were always expensive for usual users, especially end users of products that has been made by .NET technologies.

Most of the low-level customers prefer to use Linux as their OS and before .NET Core they would not like to use Microsoft technologies, despite the great abilities of them. But after .NET Core production, this problem is solved completely and we can satisfy our customers without considering their OS, etc.

Answer 2

The current documentation has a good explanation of what .NET Core is, areas to use and so on. The following characteristics best define .NET Core:

Flexible deployment: Can be included in your app or installed side-by-side user- or machine-wide.

Cross-platform: Runs on Windows, macOS and Linux; can be ported to other OSes. The supported operating systems (OSes), CPUs and application scenarios will grow over time, provided by Microsoft, other companies, and individuals.

Command-line tools: All product scenarios can be exercised at the command-line.

Compatible: .NET Core is compatible with .NET Framework, Xamarin and Mono, via the .NET Standard Library.

Open source: The .NET Core platform is open source, using MIT and Apache 2 licenses. Documentation is licensed under CC-BY. .NET Core is a .NET Foundation project.

Supported by Microsoft: .NET Core is supported by Microsoft, per .NET Core Support

And here is what .NET Core includes:

A .NET runtime, which provides a type system, assembly loading, a garbage collector, native interoperability and other basic services.

A set of framework libraries, which provide primitive data types, application composition types and fundamental utilities.

A set of SDK tools and language compilers that enable the base developer experience, available in the .NET Core SDK.

The 'dotnet' application host, which is used to launch .NET Core applications. It selects the runtime and hosts the runtime, provides an assembly loading policy and launches the app. The same host is also used to launch SDK tools in much the same way.

Answer 3

Microsoft recognized the future web open source paradigm and decided to open .NET to other operating systems. .NET Core is a .NET Framework for Mac and Linux. It is a “lightweight” .NET Framework, so some features/libraries are missing.

On Windows, I would still run .NET Framework and Visual Studio 2015. .NET Core is more friendly with the open source world like Node.js, npm, Yeoman, Docker, etc.

You can develop full-fledged web sites and RESTful APIs on Mac or Linux with Visual Studio Code + .NET Core which wasn't possible before. So if you love Mac or Ubuntu and you are a .NET developer then go ahead and set it up.

For Mono vs. .NET Core, Mono was developed as a .NET Framework for Linux which is now acquired by Microsoft (company called Xamarin) and used in mobile development. Eventually, Microsoft may merge/migrate Mono to .NET Core. I would not worry about Mono right now.

Answer 4

I was trying to create a new project in Visual Studio 2017 today (recently upgraded from Visual Studio 2015) and noticed new set of choices for the type of project. Either they're new or it's been a while since I started a new project!! :)

I came across this documentation link and found it very useful, so I am sharing. The details of the bullets are also provided in the article. I am just posting bullets here:

You should use .NET Core for your server application when:

You have cross-platform needs.
You are targeting microservices.
You are using Docker containers.
You need high performance and scalable systems.
You need side by side of .NET versions by application.

You should use .NET Framework for your server application when:

Your application currently uses .NET Framework (recommendation is to extend instead of migrating)
You need to use third-party .NET libraries or NuGet packages not available for .NET Core.
You need to use .NET technologies that are not available for .NET Core.
You need to use a platform that doesn’t support .NET Core.

This link provides a glossary of .NET terms.

EDIT 10/7/2020 Check out .NET 5.0 - "... just one .NET going forward, and you will be able to use it to target Windows, Linux, macOS, iOS, Android, tvOS, watchOS and WebAssembly and more" It's supposed to be released November 2020.

Answer 5

Microsoft just announced .NET Core v 3.0, which is a much-improved version of .NET Core.

For more details visit this great article: Difference Between .NET Framework and .NET Core from April 2019.

Answer 6

It is a sub-set of the .NET Framework, started with the Compact Framework edition. It progressed into Silverlight, Windows Store and Windows Phone. It focused on keeping the deployment small, suitable for quick downloads and devices with limited storage capabilities. And it is easier to bring up on non-Windows platforms, and surely this was the reason it was chosen as the open sourced edition. The "difficult" and "expensive" parts of the CLR and the base class libraries are omitted.

Otherwise, it is always easy to recognize when you target such a framework version, because lots of goodies will be missing. You'll be using a distinct set of reference assemblies that only expose what is supported by the runtime. It is stored on your machine in the C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETCore directory.

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Update: after the .NET Core 2.0 release I've seen some representative numbers that gives a decent insight. They have been hard at work back-porting framework APIs to .NET Core over the past two years. .NET Core 1.0 originally supported 13,000 APIs. .NET Core 2.0 added 20,000 APIs, bringing the total to 32,000 and allowing about 70% of existing NuGet packages to be ported. There are a set of APIs that are too heavily wedded to Windows to be easy to port to Linux and MacOS. Covered by the recently released Windows Compatibility Pack, it adds another 20,000 APIs.