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.






Comments are closed. Login to edit/delete your existing comments

  • 王宏亮 0

    Windows controls removal is really a bad idea,why not marking those controls obsolete and adding new ones to achieve maximum
    backward compatibility? Many applications depend on the third libraries, and those libraries depend on removed controls,thus upgrades
    are greatly hindered, even impossible.

    • Olia GavryshMicrosoft employee 0

      We are working with the control vendors on mitigating those issues and hopefully they will have the support for it very soon.

      • VB User1 0

        I can’t agree with the removal of controls.
        Please restore it.
        I hate the look of alternative controls.
        Motivation to .NET Core dropped at a stretch.

        • Olia GavryshMicrosoft employee 0

          Unfortunately we cannot continue to innovate in the .NET Core WinForms with these controls, they would challenge such features as high DPI, accessibility, and reliability. The controls were considered obsolete for 14 years already. We left them for compatibility only, keeping in mind that eventually we will move to the new controls completely.

          We saw many people have upgraded and been happy with the new alternatives. So maybe give them a chance? 🙂 But if you want to keep using the old controls, you can totally stay on .NET Framework, which is not going anywhere and will be supported. .NET Core is a new, fast developing platform that enables all the latest improvements and innovations, and in order for us to keep it that way we had to clean up the code from some obsolete parts. Sorry that it impacted you.

  • Sadiqur Rahman 0

    windows Server Requirement for .net core 3.1 is 2012 r2 sp1+. But I do not find any service pack for 2012 r2. My server OS is the 2012 r2 datacenter. Can I run .net core 3.1 on this server?

    • Richard LanderMicrosoft employee 0

      I updated the requirement to just “2012 R2”. Sorry about that. The main take-away is that we don’t support Windows Server 2008 anymore. You need to use .NET Core 2.1 if you want support for Windows Server 2008.

  • Денис Перевозчиков 0

    When will it be available via apt on Ubuntu 18.04?

    sudo apt list dotnet-sdk*
    Listing… Done
    dotnet-sdk-2.1/bionic 2.1.802-1 amd64
    dotnet-sdk-2.1.105/bionic 2.1.105-1 amd64
    dotnet-sdk-2.1.200/bionic 2.1.200-1 amd64
    dotnet-sdk-2.1.201/bionic 2.1.201-1 amd64
    dotnet-sdk-2.1.202/bionic 2.1.202-1 amd64
    dotnet-sdk-2.1.300-preview2-008533/bionic 2.1.300-preview2-008533-1 amd64
    dotnet-sdk-2.1.300-rc1-008673/bionic 2.1.300-rc1-008673-1 amd64
    dotnet-sdk-2.2/bionic,now 2.2.402-1 amd64 [installed]
    dotnet-sdk-3.0/bionic,now 3.0.101-1 amd64 [installed]

    • Rehan Saeed 0


      apt search dotnet-sdk does not show 3.1.

      • Wil Wilder Apaza Bustamante 0

        this comment has been deleted.

    • Kamran Shahid 0

      2.1 will be supported till 2021 as it was a long term release
      3.0 will be probably supported till 2020 November as it is a maintenance release.
      3.0 should ideally be converted to 3.1 as there seems no breaking change

      • Michael Hauer 0

        At least your assumptions about 3.0 is wrong, as a current version is only supported up to 3 months after a LTS release. So 3.0 has probably the 3/3 as EOL

  • Oliver Weichhold 0

    As someone working on Net Core projects that often have to invoke C/C++ libraries for performance reasons on Windows and Linux, it would be fantastic if C++/CLI would be supported cross-platform. PInvoke is a workaround but C++/CLI is so much nicer.

    • Richard LanderMicrosoft employee 0

      I hear you. We have no plans to build that. We added C++/CLI for compatibility reasons only.

  • Jon Miller 0

    Still no support for ASP.NET Web Forms. Thanks Microsoft. And thanks for making the latest EF Core not work work with it either.

    • Jon Miller 0

      I take back what I said about the latest EF Core not working with it. I see that support for it on .NET Framework has been reintroduced. Thank you! However, I am still unthankful for ASP.NET Web Forms not being moved forward onto .NET Core. Scott Guthrie designed it right back in 2000. It works and it has been a productive way to develop applications ever since then.

      • Richard LanderMicrosoft employee 0

        And it will keep on working for you, for a long-time, on .NET Framework.

        We are never going to enable web forms on .NET Core. Blazor is our new story for a similar kind of experience and people are super happy with it. I understand why you are unhappy. However, we’ve got a new solution that is aligned with modern patterns that a high percentage of .NET users are happy with. In the aggregate, that’s a winning proposition.

        • Jon Miller 0

          Except that new language features aren’t going into .NET Framework. It will be years before Blazor has matured. Why don’t you develop a robust set of UI controls for it? You would have me sold if you did that. You won’t do it though.

          • Jon 0

            Realistically Web Forms was dead almost a decade ago when they renamed ASP.NET to ASP.NET MVC, and I say good riddance. If you review the history of Web Forms, it saw almost no changes after MVC showed up. There’s nothing wrong with MVVM per se, but Web Forms allows — and almost encourages — a lot of truly awful development practices (and if you’ve worked with lowest-bidder contractor code, you’ll have seen the worst of the worst). I’ve been doing large enterprise-style server-side Blazor POCs and it’s mostly a joy to work with. My only complaint is that they haven’t put a near-term end-of-life date on the .NET Framework itself.

          • Jon Miller 0

            Does Blazor have an editable combobox? Does it have a grid control with built-in filtering, sorting, grouping, and inline editing? Let me know when it does and maybe I will be the biggest booster of it. MVC lacked from day one due to the simple fact that it lacked the concept of UI controls. It depends on what kind of app you are developing, if you are developing something like an UI, no, you don’t need robust UI controls, at least not for the read-only parts of it. However, that doesn’t describe the requirements for all applications that are out there. I strongly disagree with those who think you need to program web apps at the bare metal. You should write apps at the proper level of abstraction. Web Forms does that and always has. MVC never did. I am an application developer. I want to focus on the business logic that I am tasked with developing, not developing my own UI controls. I will be extremely surprised if Microsoft includes robust UI controls in Blazor. If they do, they will have a winner. One should not have to rely on third party UI controls at this late date. The ease of application development should be getting better. Maybe it will eventually with Blazor, but, it has been an abject failure for about the last 10 years. Luckily, I was able to avoid 99% of the JavaScript and web API hell that the experts are inflicting on everyone, by simply staying the course and not being a lemming following bad ideas.

  • Steven Chapman 0

    When I install dotnet-hosting-3.1.0-win.exe, It installs the 3.1.0 Preview 3 runtime, not the RTM.

  • Sarathlal Saseendran 0

    When I installed 3.1 SDK (Installed Visual Studio 2019 v 16.4), I have noticed that 3.0 is no more available in my machine. Is it a normal behavior? Please advise.

  • Athanasios Ioannidis 0

    Just updated to VS 2019 16.4. My core 3.0 framework depended app now fails with a 500.30 ACNM error. I installed, uninstalled and reinstalled 3.1 hosting bundle, but nothing works. I updated the projects and all the nuget packages to 3.1, and still the process cannot start. Debugging with F5 actually enters the process and fails a few moments later. The only message I could see was a null reference exception deep within a system assembly.

    On the other side, a brand new 3.1 (or 3.0) web site starts normally.

    Is this connected with the preview3 problem?

  • SuperCocoLoco . 0

    Completely lacking Visual Basic.NET support.

    • Steve 0

      VB.NET console and test projects are completely supported, however, due to lacking of VB desktop runtime on .NET Core (which is still under development), there’s no support to winforms and WPF for VB.NET currently.

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