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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.
- Use xmm for stack prolog – dotnet/runtime #32538 — Change to x86/x64 prolog zeroing code. Improvements: Json; TechEmpower. Credit: Ben Adams.
- Add ValueNumbering support for GT_SIMD and GT_HWINTRINSIC tree nodes – dotnet/runtime #31834 — Enable the optimizer for SIMD and hardware intrinsic types.
- Use GT_NULLCHECK for unconsumed indirections – dotnet/runtime #32641 — Remove redundant null checks.
- invoke nullable box optimizations earlier – dotnet/runtime #32269 — Improve optimizations for
Nullable<T>. - Optimize range checks for various array index patterns – dotnet/runtime #1644 — Improvement in range check elimination.
- Optimize
obj.GetType() != typeof(X)for sealed classes – dotnet/runtime #32790 — Improvement to type check expression. - Eliminate duplicate zero initializations more aggressively – dotnet/runtime #31960 — Better and broader approach for eliminating duplicate zero initializations.
- Fix method and basic block flags used by early opts – dotnet/runtime #2196 – Enables certain optimization to be used more often. For example, replacing array length with a constant now occurs much more often.
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
- Card mark stealing – dotnet/coreclr #25986 — Server GC (on different threads) can now work-steal while marking gen0/1 objects held live by older generation objects. This means that ephemeral GC pauses are shorter for scenarios where some GC threads took much longer to mark than others.
- Introducing Pinned Object Heap – dotnet/runtime #32283 — Implemented part of the POH (Pinned Object Heap) feature – the part internal to GC. This new heap (essentially a peer to LOH) will allow the GC to manage pinned objects separately, and as a result avoid the negative effects of pinned objects on the generational heaps.
- Allow allocating large object from free list while background sweeping SOH – dotnet/runtime #2103 — Enabled LOH allocations using the free list while BGC is sweeping SOH. Previously this was only using end of segment space on LOH. This allowed for better heap usage.
- Background GC suspension fixes – dotnet/coreclr #27729 — Suspension fixes to reduce time for both BGC and user threads to be suspended. This reduces the total time it takes to suspend managed threads before a GC can happen. dotnet/coreclr #27578 also contributes to the same outcome.
- Fix named cgroup handling in docker – dotnet/runtime #980 — Added support to read limits from named cgroups. Previously we only read from the global one.
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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Will the Xamarin built on .Net 5 continue to use it’s own Xaml or WPF’s or UWP? And am I correct in my understanding that Mono is being dropped and that .Net Core will be the base of .Net 5?
Hello Team,
Any cross platform UI for Desktop, Web, Mobile????
It would be super great if .Net provide cross platform UI.
Can I have some details on the winforms webbrowser control in .NET 5 is it still based on IE. will .net 5 winform support custom controls?
I keep reading that .Net 5 is a unification of .Net Framework and .Net Core, ahm, what about .Net UWP – I hope UWP devs can use .Net 5 the same as everybody else and target Win32+UWP for release with the click of a button. The situation now isn’t good, with .Net UWP years behind everybody else and stuck on C# 7.2 and almost no development of the platform.
Great stuff! .NET just keeps getting better and better!!
This is awesome, thank you.
Hi,
What’s about VB.NET and WindowsForms ?
I read that they will be included with Core 5. ? Is it true ? Is it now or in future ?
Take care for you and yours
Best regards
Hi guys,
We are unable to restore the latest preview version of Windows Compatibility Pack (5.0.0-preview.2.20160.6) in .Net 5 WPF application. Should this work at the moment or it is known issue?
Regards,
Kalin
Telerik
Kalin, thanks for pointing to this problem. We’ll investigate it and get back to you!
This issue will be fixed in Preview 3. Meanwhile as a workaround you can reference needed libraries directly or use the older version of the compatibility pack. We added the description to the known issues
Any news about cross-platform UI stack atop .NET 5.0?
Hey Alexey, is Blazor what you’re looking for? Presently an ASP.NET web technology but MS demonstrate native app with it as experiments too. Google “Steve Sanderson Blazor” to find out more.
People keep asking this, and MS keep answering: There is no good way to make a cross platform UI, unless you write a platform-independent library. Winforms is a wrapper around Win32 API, and WPF use DirectX to draw on screen, both Windows-only technologies.
When people are asking MS about “cross-platform UI stack atop .NET 5.0” – it’s of course not about EXISTING WinForms or WFP implementations. It is a more like “how your work on a NEW cross-platform UI technology (maybe XAML-based or any other type) is going for now”? MS started a survey not long after .NET 5 was announced (about aspects of NEW cross-platform UI technology) – so we are asking about current progress..
Yes. Cross-platform UI stack atop a .net 5.0, is what MS must consider on priority, since it’s the UI that all end-users need to interact with an application; whether be it windows, web or mobile.
Trying out this preview on various projects. Performance is about 20% down overall vs Net Core 3.1. I’m sure perf optimization comes later but this is where is is at the moment.