Announcing .NET Core 3.1

Rich Lander [MSFT]

Announcing .NET Core 3.1

We’re excited to announce the release of .NET Core 3.1. It’s really just a small set of fixes and refinements over .NET Core 3.0, which we released just over two months ago. The most important feature is that .NET Core 3.1 is an long-term supported (LTS) release and will be supported for three years. As we’ve done in the past, we wanted to take our time before releasing the next LTS release. The extra two months (after .NET Core 3.0) allowed us to select and implement the right set of improvements over what was already a very stable base. .NET Core 3.1 is now ready to be used wherever your imagination or business need takes it.

You can download .NET Core 3.1, for Windows, macOS, and Linux:

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

Visual Studio 2019 16.4 was also released today and includes .NET Core 3.1. It is a required update to use .NET Core 3.1 with Visual Studio. For Visual Studio 2019 users, we recommend simply updating Visual Studio to 16.4 and instead of separately downloading .NET Core 3.1.

Visual Studio for Mac also supports and includes .NET Core 3.1, in the Visual Studio for Mac 8.4 Preview channel. You will need to opt into the Preview channel to use .NET Core 3.1.

Release notes:

The changes in .NET Core 3.1 were primarily focussed on Blazor and Windows Desktop, the two new and large additions in .NET Core 3.0. This includes support for C++/CLI, which has been a regular request for developers targeting Windows.

Before we take a look at what’s new in .NET Core 3.1, let’s take a quick look at the key improvements in .NET Core 3.0, which is the bulk of what’s important to consider for .NET Core 3.1.

Recap of .NET Core 3.0 Improvements

The following key improvements were delivered in .NET Core 3.0. We’ve already heard from developers of big sites that it is working super well for them.

  • .NET Core 3.0 is already battle-tested by being hosted for months at and on Many other Microsoft teams will soon be deploying large workloads on .NET Core 3.1 in production.
  • Performance is greatly improved across many components and is described in detail at Performance Improvements in .NET Core 3.0 and Hardware Intrinsics in .NET Core.
  • C# 8 add async streams, range/index, more patterns, and nullable reference types. Nullable enables you to directly target the flaws in code that lead to NullReferenceException. The lowest layer of the framework libraries has been annotated, so that you know when to expect null.
  • F# 4.7 focuses on making some thing easier with implicit yield expressions and some syntax relaxations. It also includes support for LangVersion, and ships with nameof and opening of static classes in preview. The F# Core Library now also targets .NET Standard 2.0. You can read more at Announcing F# 4.7.
  • .NET Standard 2.1 increases the set of types you can use in code that can be used woth both .NET Core and Xamarin. .NET Standard 2.1 includes types since .NET Core 2.1.
  • Windows Desktop apps are now supported with .NET Core, for both Windows Forms and WPF (and open source). The WPF designer is part of Visual Studio 2019. The Windows Forms designer is in preview and available as a download.
  • .NET Core apps now have executables by default. In past releases, apps needed to be launched via the dotnet command, like dotnet myapp.dll. Apps can now be launched with an app-specific executable, like myapp or ./myapp, depending on the operating system.
  • High performance JSON APIs have been added, for reader/writer, object model and serialization scenarios. These APIs were built from scratch on top of Span<T> and use UTF8 under the covers instead of UTF16 (like string). These APIs minimize allocations, resulting in faster performance, and much less work for the garbage collector. See Try the new System.Text.Json APIs.
  • The garbage collector uses less memory by default, often a lot less. This improvement is very beneficial for scenarios where many applications are hosted on the same server. The garbage collector has also been updated to make better use of large numbers of cores, on machines with >64 cores. See Making CPU configuration better for GC on machines with > 64 CPUs.
  • .NET Core has been hardened for Docker to enable .NET applications to work predictably and efficiently in containers. The garbage collector and thread pool have been updated to work much better when a container has been configured for limited memory or CPU. .NET Core docker images are smaller, particularly the SDK image. See: Running with Server GC in a Small Container Scenario Part 0, Running with Server GC in a Small Container Scenario Part 1 – Hard Limit for the GC Heap and Using .NET and Docker Together – DockerCon 2019 Update.
  • Raspberry Pi and ARM chips are now supported to enable IoT development, including with the remote Visual Studio debugger. You can deploy apps that listen to sensors, and print messages or images on a display, all using the new GPIO APIs. ASP.NET can be used to expose data as an API or as a site that enables configuring an IoT device.

Platform support

.NET Core 3.1 is supported on the following operating systems:

  • Alpine: 3.10+
  • Debian: 9+
  • Ubuntu: 16.04+
  • Fedora: 29+
  • centOS: 7+
  • RHEL: 6+
  • openSUSE: 15+
  • SUSE Enterprise Linux (SLES): 12 SP2+
  • macOS: 10.13+
  • Windows Client: 7, 8.1, 10 (1607+)
  • Windows Server: 2012 R2+

Note: Windows Forms and WPF apps are only functional and supported on Windows.

Chip support follows:

  • x64 on Windows, macOS, and Linux
  • x86 on Windows
  • ARM32 on Windows and Linux
  • ARM64 on Linux (kernel 4.14+)

Note: Please ensure that .NET Core 3.1 ARM64 deployments use Linux kernel 4.14 version or later. For example, Ubuntu 18.04 satisfies this requirement, but 16.04 does not.

Windows Forms Controls Removal

The following Windows Forms controls have been removed from .NET Core 3.1:

  • DataGrid
  • ToolBar
  • ContextMenu
  • Menu
  • MainMenu
  • MenuItem

These controls were replaced with more powerful controls in .NET Framework 2.0, back in 2005. They have not been available by default in the Visual Studio Designer Toolbox for many years. As a result, we decided to remove these controls and focus only on the new ones.

The following replacements are recommended:

Old Control (API) Recommended Replacement Other associated APIs removed
DataGrid DataGridView DataGridCell, DataGridRow, DataGridTableCollection, DataGridColumnCollection, DataGridTableStyle, DataGridColumnStyle, DataGridLineStyle, DataGridParentRowsLabel, DataGridParentRowsLabelStyle, DataGridBoolColumn, DataGridTextBox, GridColumnStylesCollection, GridTableStylesCollection, HitTestType
ToolBar ToolStrip ToolBarAppearance
ToolBarButton ToolStripButton ToolBarButtonClickEventArgs, ToolBarButtonClickEventHandler, ToolBarButtonStyle, ToolBarTextAlign
ContextMenu ContextMenuStrip
Menu ToolStripDropDown, ToolstripDropDownMenu MenuItemCollection
MainMenu MenuStrip
MenuItem ToolstripMenuItem

Yes, this is an unfortunate breaking change. You will see build breaks if you are using the controls we removed in your applications. Also, if you open .NET Core 3.0 applications in the latest versions of the .NET Core Windows Forms designer, you will see errors if you are using these controls.

We recommend you update your applications to .NET Core 3.1 and move to the alternative controls. Replacing the controls is a straight-forward process, essentially “find and replace”.

First, we should have made these changes before we released .NET Core 3.0, and we appologize for that. We try to avoid late changes, and even more for breaking changes, and it pains us to make this one.

As we got further into the Windows Forms designer project, we realized that these controls were not aligned with creating modern applications and should never have been part of the .NET Core port of Windows Forms. We also saw that they would require more time from us to support than made sense.

Our goal is to continue to improve Windows Forms for high DPI, accessibility, and reliability, and this late change was required to enable us to focus on delivering that.


We added support for creating C++/CLI (AKA “managed C++”) components that can be used with .NET Core 3.0+, in Visual Studio 2019 16.4. You need to install the “Desktop development with C++” workload and the “C++/CLI support” component in order to use C++/CLI.

This component adds a couple templates that you can use:

  • CLR Class Library (.NET Core)
  • CLR Empty Project (.NET Core)

If you cannot find them, just search for them in the New Project dialog.

C++/CLI is only enabled on Windows. You cannot use C++/CLI components targeted for .NET Framework with .NET Core or vice versa.


We recommend moving to .NET Core 3.1 as soon as you can. It is a great release (largely due to 3.0) that brings improvements to so many aspects of .NET Core. It is also a long term support (LTS) release, and will be supported for three years.

Life cycle update:

  • .NET Core 3.0 will reach end-of-life three months from today, on March 3, 2020.
  • .NET Core 2.2 will each end of life on December 23rd.
  • .NET Core 2.1 will be supported until August 2021 (it is also an LTS release).

The following .NET Core posts are recommended reading to learn more about what you get with .NET Core 3.1 and other projects we’ve been working on.






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  • Nitin Sawant 0

    This may not be the right place to ask this
    .net core runs on
    windows – ok
    max – ok
    linux – ok

    why not android??? after all its linux too

    • Nitin Sawant 0

      I know xamarin but here I am talking about native support for .net apps

    • Richard LanderMicrosoft employee 0

      People have had success running .NET Core on Android in limited scenarios. There is a LOT more to running on Android than just Linux, if you want to write an actual Android application. That’s what we have Xamarin for. It’s a whole product above and beyond what .NET Core can do.

  • Kenneth Carter 0

    updating visual studio 2019 installed .net core 3.1 but wiped clean and corrupted the 2.1, 2.2 .net core installs. now the .net core 2.2 app I was working on will not run unit tests because the 2.2 sdk is no longer there.

    • Richard LanderMicrosoft employee 0

      Can you share some of the error messages? Is it maybe due to using global.json?

  • Jeff Johnson 0

    Please update azure pipelines to support .net core 3.1, thanks so much for your hard work on this release.

    • Tyler 0

      They are updated now (though you probably know this by now).

  • Karl X 0

    Following the instructions here: I still only see preview3.

    apt-cache show dotnet-runtime-3.1
    Package: dotnet-runtime-3.1
    Priority: standard
    Section: libs
    Installed-Size: 71059
    Maintainer: .NET Core Team
    Architecture: amd64
    Version: 3.1.0-1
    Depends: dotnet-hostfxr-3.1 (>= 3.1.0), dotnet-runtime-deps-3.1 (>= 3.1.0)
    Filename: pool/main/d/dotnet-runtime-3.1/dotnet-runtime-3.1.0-x64.deb
    Size: 21764038
    MD5sum: d224731e908efaf2af884c49002c8649
    SHA1: e0ae40d1d433033adaf666b8cc5a40ed8101903b
    SHA256: 4df4f5a8eeb62f211f323912d1af87ddb4c560f85f991c2db3cddec61de7a6c5
    SHA512: 7b32079d8b53a1d104ea36e90164b684a6e888228fc1c0db29f133d4b0bc1fb2c2a937cd9f73ffbfe575566758ea3306abcb69561a54abbcf70186a21159bd2a
    Description: Microsoft .NET Core Runtime – 3.1.0 Preview 3 Microsoft.NETCore.App 3.1.0
    .NET Core is a development platform that you can use to build command-line applications, microservices and modern websites. It is open source, cross-platform and is supported by Microsoft. We hope you enjoy using it! If you do, please consider joining the active community of developers that are contributing to the project on GitHub ( We happily accept issues and PRs.
    Description-md5: b7dfb35a3c6552225d0f65dedcbbfbbf

    • Davis GoodinMicrosoft employee 0

      This is an issue with the description, that package should install a 3.1.0 runtime fine. If you run “dotnet –info”, you should see 3.1.0. I’ve opened to track this and there’s some more info about the problem there.

      Editing to add: this problem will be fixed in 3.1.1.

  • Dimitri Samorukov 0

    i have problems with compiling of WPF applications for windows desktop, with then new version of Visual Studio ( Professional 2019
    Version 16.4.0 ) After update and creating a new WPF-Project, i get following error:

    1>C:\Program Files (x86)\dotnet\sdk\3.1.100\Sdks\Microsoft.NET.Sdk.WindowsDesktop\targets\Microsoft.WinFX.targets(225,9): error MSB4062: The Microsoft.Build.Tasks.Windows.MarkupCompilePass1 task could not be loaded from the C:\Program Files %28×86%29\dotnet\sdk\3.1.100\Sdks\Microsoft.NET.Sdk.WindowsDesktop\tools\net472\PresentationBuildTasks.dll assembly. The file or assembly “file:///C:\Program Files %28×86%29\dotnet\sdk\3.1.100\Sdks\Microsoft.NET.Sdk.WindowsDesktop\tools\net472\PresentationBuildTasks.dll” or a dependency on it was not found. The system cannot find the specified file. Make sure that the declaration is correct, the assembly and all associated dependencies are available, and the task contains a public class that implements Microsoft.Build.Framework.ITask.

    .net SDK 3.1.100 is installed and is available under the given path, the operation system and visual studio are using the german language.
    What ist the problem here ?

  • Pericles J. Otero 0

    I would like to know if Visual Basic for windows forms desktop has not been included in .NET core 3.1 and if it will still have any updates that will include soon or MS has no interest?

  • Raghavendra Rao Itikarlapalli 0

    Earlier we’ve used .NET Core 2.2.105 to build our applications using the below command.
    dotnet publish –configuration Release –force –output publish ABC.sln
    This ultimately created a publish folder and we used to copy contents from that folder. But recently we’ve upgraded it to .NET Core 3.1.100 and it failed to generate this publish folder.

    Is there any additional parameter that we need to provide in order to create a publish folder?

  • ozbobWA 0

    typo: woth both

  • Hiroyuki Yamada 0

    I’d like to use System.Windows.Threading.Dispatcher in C++/CLI.
    But I can’t find any Framework to add reference.
    Is there any way that could?

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