Announcing .NET 5.0 Preview 2

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Richard

Today, we’re releasing .NET 5.0 Preview 2. It contains a set of smaller features and performance improvements. We’re continuing to work on the bigger features that will define the 5.0 release, some of which are starting to show up as initial designs at dotnet/designs. The .NET 5.0 Preview 1 post covers what we are planning on building for .NET 5.0. Please take a look at the post and the designs repository and share any feedback you have. And, of course, please install Preview 2, and test any workloads you can with it.

You can download .NET 5.0 Preview 2, for Windows, macOS, and Linux:

ASP.NET Core and EF Core are also being released today.

You need to use Visual Studio 2019 16.6 to use .NET 5.0. Install the latest version of the C# extension, to use .NET 5.0 with Visual Studio Code. Visual Studio for Mac isn’t yet supported.

Release notes:

Let’s look at some of the improvements in Preview 2.

Code quality improvements in RyuJIT

Every release includes a set of changes that improve the machine code that the JIT generates (we call this “code quality”). Better code quality means better performance. In summary, about half of the following improvements are actual new optimizations and the other half are due to changing the flow of RyuJIT to enable existing optimizations to apply to more code patterns.

If you like this style of improvement or are an ARM64 user, you may be interested in Vectorise BitArray for ARM64, coming soon (already merged, but not in Preview 2). This change demonstrates a lot of focus on ARM64 in .NET 5.0.

Garbage Collector

Closing

Please take a moment to try out Preview 2, possibly in a container, a VM. We’d like your feedback on the quality of the release. There is a lot more coming, over the next several months, leading up a November release.

We’re running 50% of the .NET Website traffic on .NET 5.0 as a test case, using Azure load balancing. We’ve been doing that since days after we released Preview 1. You may remember us doing something similar with .NET Core 3.0 and 3.1. By splitting the traffic 50/50, we can ensure that 5.0 gets consistently better with constant performance data available to us. This model keeps us honest, and it’s also a great testing approach. We trust our most important site with ALL of our previews, in production (which we don’t recommend for anyone else). That should make adopting our final release a pretty easy choice for you. The version number is in the footer of .NET website; feel free to check at any time.

Stepping back for a minute, many of you might be interested in how the the folks on the .NET Team at Microsoft are doing. We’re doing well. We have lots of Teams meeting every day to organize and support one another, and are just as active on GitHub as ever. The team is close-knit, and collaborating across multiple time-zones. We’re all focused on this release, and very much intending to deliver what we set out to deliver when we first defined our plans, after releasing .NET Core 3.0. Take care.

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