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Announcing .NET 5.0

We’re excited to release .NET 5.0 today and for you to start using it. It’s a major release — including C# 9 and F# 5 — with a broad set of new features and compelling improvements. It’s already in active use by teams at Microsoft and other companies, in production and for performance testing. Those teams are showing us great results that demonstrate performance gains and/or opportunities to reduce hosting costs for their web applications. We’ve been running our own website on 5.0 since Preview 1. From what we’ve seen and heard so far, .NET 5.0 delivers significant value without much effort to upgrade. It’s a great choice for your next app, and a straightforward upgrade from earlier .NET Core versions. We hope you enjoy using it, on your desktop, laptop, and cloud instances.

ASP.NET Core, EF Core, C# 9, and F# 5 are also being released today. .NET Conf 2020 — our free and virtual conference — is being held today so you can learn about all of the new releases.

You can download .NET 5.0, for Windows, macOS, and Linux, for x86, x64, Arm32, Arm64.

Installers and binaries
Container images
Linux packages
Release notes
Known issues
GitHub issue tracker
.NET 5.0 Contributors
For Visual Studio users, you need Visual Studio 16.8 or later to use .NET 5.0 on Windows and the latest version of Visual Studio for Mac) on macOS. The C# extension for Visual Studio Code already supports .NET 5.0 and C# 9.

.NET 5.0 is the first release in our .NET unification journey. We built .NET 5.0 to enable a much larger group of developers to migrate their .NET Framework code and apps to .NET 5.0. We’ve also done much of the early work in 5.0 so that Xamarin developers can use the unified .NET platform when we release .NET 6.0. There is more on .NET unification, later in the post.

Now is a good time to call out the incredible collaboration with everyone contributing to the .NET project. This release marks the fifth major .NET version as an open source project. There is now a large mix of individuals and small and large companies (including the .NET Foundation corporate sponsors) working together as a large community on various aspects of .NET in the dotnet org on GitHub. The improvements in .NET 5.0 are the result of many people, their effort, smart ideas, and their care and love for the platform, all above and beyond Microsoft’s stewardship of the project. From the core team working on .NET every day, we extend a very large “thank you” to everyone that contributed to .NET 5.0 (and previous releases)!

We introduced .NET 5.0 way back in May 2019, and even set the November 2020 release date at that time. From that post: “we will ship .NET Core 3.0 this September, .NET 5 in November 2020, and then we intend to ship a major version of .NET once a year, every November”. You’d think that “November 2020” was a cheque that could not be cashed given all the challenges this year, however, .NET 5.0 has been released on time. Thanks to everyone on the team that made that happen! I know it has not been easy. Looking forward, you should expect .NET 6.0 in November 2021. We intend to release new .NET versions every November.

The rest of the blog is dedicated to highlighting and detailing most of the improvements in .NET 5.0. There is also an update on our .NET unification vision.

.NET 5.0 Highlights
There are many important improvements in .NET 5.0:

.NET 5.0 is already battle-tested by being hosted for months at and (version).
Performance is greatly improved across many components and is described in detail at Performance Improvements in .NET 5.0, Arm64 Performance in .NET 5.0, and gRPC.
C# 9 and F# 5 offer new language improvements such as top-level programs and records for C# 9, while F# 5 offers interactive programming and a performance boost for functional programming on .NET.
.NET libraries have enhanced performance for Json serialization, regular expressions, and HTTP (HTTP 1.1, HTTP/2). They are also are now completely annotated for nullability.
P95 latency has dropped due to refinements in the GC, tiered compilation, and other areas.
Application deployment options are better, with ClickOnce client app publishing, single-file apps, reduced container image size, and the addition of Server Core container images.
Platform scope expanded with Windows Arm64 and WebAssembly.
I’ve written many samples for the .NET 5.0 preview posts. You might want to take a look at .NET 5.0 Examples to learn more about new C# 9 and libraries features.

Platform and Microsoft Support
.NET 5.0 has a nearly identical platform support matrix as .NET Core 3.1, for Windows, macOS, and Linux. If you are using .NET Core 3.1 on a supported operating system, you should be able to adopt .NET 5.0 on that same operating system version for the most part. The most significant addition for .NET 5.0 is Windows Arm64.

.NET 5.0 is a current release. That means that it will be supported for three months after .NET 6.0 is released. As a result, we expect to support .NET 5.0 through the middle of February 2022. .NET 6.0 will be an LTS release and will be supported for three years, just like .NET Core 3.1.

Unified platform vision
Last year, we shared a vision of a unified .NET stack and ecosystem. The value to you is that you will be able to use a single set of APIs, languages, and tools to target a broad set of application types, including mobile, cloud, desktop, and IoT. You might realize that you can already target a broad set of platforms with .NET today, however, the tools and APIs are not always the same across Web and Mobile, for example, or released at the same time.

As part of .NET 5.0 and 6.0, we are unifying .NET into a single product experience, while enabling you to pick just the parts of the .NET platform that you want to use. If you want to target Mobile and not WebAssembly, you don’t need to download the WebAssembly tools, and vice versa. Same with ASP.NET Core and WPF. You’ll also have a much easier way to acquire all the .NET tools and build and runtime packs that you need from the command line. We’re enabling a package manager experience (including using existing package managers) for .NET platform components. That will be great for many scenarios. Quick construction of a development environment and CI/CD will probably be the biggest beneficiaries.

We had intended to deliver the entirety of the unification vision with .NET 5.0, but in the wake of the global pandemic, we had to adapt to the changing needs of our customers. We’ve been working with teams from companies from around the world that have needed help to speed up their adoption of cloud technologies. They, too, have had adapt to the changing needs of their customers. As a result, we are delivering the vision across two releases.

The first step towards this vision was consolidating .NET repos, including a large subset of Mono. Having one repo for the runtime and libraries for .NET is a precondition to delivering the same product everywhere. It also helps with making broad changes that affect runtime and libraries, where there were previously repo boundaries. Some people were worried that a large repo would be harder to manage. That hasn’t proven to be the case.

In the .NET 5.0 release, Blazor is best example of taking advantage of repo consolidation and .NET unification. The runtime and libraries for Blazor WebAssembly are now built from the consolidated dotnet/runtime repo. That means Blazor WebAssembly and Blazor on the server use the exact same code for List<t>, for example. That wasn’t the case for Blazor prior to .NET 5.0. The approach we took for Blazor WebAssembly is very similar to what we’ll do with Xamarin in .NET 6.0.

The .NET Framework remains a supported Microsoft product and will continue to be supported with each new version of Windows. We announced last year that we had stopped adding new features to .NET Framework and finished adding .NET Framework APIs to .NET Core. That means that now is a great time to consider moving your .NET Framework apps to .NET Core. For .NET Framework client developers, Windows Forms and WPF are supported with .NET 5.0. We’ve heard from many developers that porting from .NET Framework is straightforward. For .NET Framework server developers, you need to adopt ASP.NET Core to use .NET 5.0. For Web Forms developers, we believe that Blazor provides a similar developer experience with an efficient and much more modern implementation. WCF server and Workflow users can look to community projects that are supporting those frameworks. The porting from .NET Framework to .NET Core doc is a good place to start. That all said, keeping your app on .NET Framework is a fine approach if you are happy with your experience.

The Windows team is working on Project Reunion as the next step forward for UWP and related technologies. We’ve been collaborating with the Reunion team to ensure that .NET 5.0 and later versions will work well with WinUI and WebView2. The Project Reunion repo is the best place to stay up to date with progress.

Let’s switch to looking at what’s new in the 5.0 release.

C# 9 and F# 5 are part of the .NET 5.0 release and included in the .NET 5.0 SDK. Visual Basic is also included in the 5.0 SDK. It does not include language changes, but has improvements to support the Visual Basic Application Framework on .NET Core.

C# Source Generators are an important new C# compiler feature. They are not technically part of C# 9 since it doesn’t have any language syntax. See New C# Source Generator Samples to help you get started using this new feature. We expect to make more use of source generators within the .NET product in .NET 6.0 and beyond.

As a way to try out the new release ourselves, a few of us decided to update the dotnet/iot repo to use new C# 9 syntax and target .NET 5.0. The changes resulted in removing >2k lines of code, just by adopting new syntax. It uses top-level programs, records, patterns, and switch expressions. It has also been updated to take advantage of the complete set of nullable annotations in .NET libraries. We also updated the .NET IoT docs. We’ll take a look at few examples from that repo to explore C# 9.”

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