Announcing .NET Core 3.0 Preview 9

Rich Lander [MSFT]

Today, we’re announcing .NET Core 3.0 Preview 9. Just like with Preview 8, we’ve focused on polishing .NET Core 3.0 for a final release and aren’t adding new features. If these final builds seem less exciting than earlier previews, that’s by design.

Download .NET Core 3.0 Preview 9 right now on Windows, macOS, and Linux.

ASP.NET Core, EF Core and Visual Studio are also releasing updates today.


.NET Core 3.0 is launching at .NET Conf

Tune in for .NET Conf, September 23-25th. We will launch .NET Core 3.0 during .NET Conf. Yes, that means that Preview 9 is the last preview, and .NET Core 3.0 will be released in its final version later this month. We have a lot of great speakers and content prepared for .NET Conf this year. It’s one of the big .NET developer events each year, and you cannot beat the price. It’s free and streaming online.

Visual Studio Support

.NET Core 3.0 is supported with Visual Studio 2019 16.3 Preview 3 and Visual Studio for Mac 8.3, which were also released today. Please upgrade to it for the best (and supported) experience with .NET Core 3.0 Preview 9. See Visual Studio 2019 16.3 release notes for more information.

We know that some folks have been successful using .NET Core 3.0 builds with Visual Studio 2019 16.2 and wonder why 16.3 is required. The short answer is that we only test .NET Core 3.0 with Visual Studio 2019 16.3 and have made many improvements and key fixes that are only in 16.3. The same model applies to Visual Studio for Mac 8.3.

The C# Extension for Visual Studio Code is always updated to support new .NET Core versions. Make sure you have the latest version of the C# extension installed.

Go Live

NET Core 3.0 Preview 9 is supported by Microsoft and can be used in production. We strongly recommend that you test your app running on Preview 9 before deploying into production. If you find an issue with .NET Core 3.0, please file a GitHub issue and/or contact Microsoft support.

The Microsoft .NET Site has been updated to .NET Core 3.0 Preview 9 (see the .NET Core runtime version in the footer text). It’s been running great on previews, starting with Preview 7, on Azure WebApps (as a self-contained app). Check out the Microsoft .NET site and see for yourself how it performs on Preview 9.


The .NET Core 3.0 release is coming close to completion, and the team is solely focused on stability and reliability now that weโ€™re no longer building new features. Please tell us about any issues you find, ideally as quickly as possible. We want to get as many fixes in as possible before we ship the final 3.0 release.

If you missed earlier (more exciting) posts about .NET Core 3.0, check out the improvements that were part of .NET Core 3.0 Preview 6 (last preview with new features) and earlier releases.

If you install daily builds, read an important announcement about .NET Core master branches.


Discussion is closed. Login to edit/delete existing comments.

  • Joe Phillips 0

    Should the “Preview 6” link at the bottom say “Preview 8”? ๐Ÿ˜€

    • Richard LanderMicrosoft employee 0

      Preview 6 was the last preview with new features. I updated the text to clarify.

  • Jon 0

    The Release Notes link on the download page 404s…

    • Richard LanderMicrosoft employee 0

      This appears to be resolved. Thanks for reporting.

  • Eaton 0

    How’s work going on the WinForms designer?

    • Olia GavryshMicrosoft employee 0

      We will release a first preview version of the WinForms designer around the .NET Core 3.0 GA. It’s still very early days for the designer. This version willl support only some common controls and basic operations just to give you a sneak peek on the progress we’ve done so far. After that we will be releasing new preview versions on a regular cadence.

      • gc y 0

        Do you have any plan for WPF designer?

  • Max Mustermueller 0

    When will .NET Core 3 ship with a Windows update? That would be great to know when our customers should have it by default (ignore self contained publish in this case) just like .NET Framework.

    • Richard LanderMicrosoft employee 0

      No plans to do that. Feel free to request that @

      We are considering a .NET Core “framework package” for apps deployed via the Windows Store.

  • Dave Nay 0

    I thought .NET Core 3.0 was supposed to cleanup old installed versions proactively? I still have dozens of versions installed (including previews 6, 7, and 8) after installing P9.

    • Vidmantas Drasutis 0

      If those was installed by vs installer then yes. In other case it does not clean (from what I remember)

      • Livar CunhaMicrosoft employee 0

        .NET Core starting with SDK 3.1.100 will upgrade itself. Meaning, if you had 3.1.100 and are now adding 3.1.101, then 3.1.100 will be replaced by the newer one.
        It won’t proactively remove older versions like 2.1.x, 2.2.x, etc.

  • Tadeas Lejsek 0

    Can you please include details about C++/CLI support?

    • Livar CunhaMicrosoft employee 0

      That’s coming in .NET Core 3.1 and VS 16.4

  • Alexey Leonovich 0

    1) Does this preview support building C++/CLI projects for Windows?
    2) Does x64 .NET Core SDK installer already includes x86 or I need to install both on x64 machine? The same question for .NET Core runtimes.
    3) Is .Net Core 3 supposed to be used in offline (disconnected) scenarios? Because for now it’s impossible to compile template Windows Forms App (.NET Core) with Visual Studio 2019 Professional 16.3 preview 3 and .NET Core 3-preview9 if PC cannot reach –

    • Livar CunhaMicrosoft employee 0

      1) Coming in .NET Core 3.1 and VS 16.4
      2) VS will install the runtime for both x86 and x64 if you are on a x64 machine and installing x64 VS. It won’t install both SDKs because that’s not really necessary. You can target x86 from a x64 SDK.
      3) That should work. That VS feedback item is for preview3. What error exactly are you getting with preview9? You should see a restore failure if there is any package missing, which should not be the case for a vanilla winforms project targeting net core.

  • Sergey Litvinov 0

    Is there a reason why doesn’t have any preview packages including preview9? Or it will be there only after full release?

  • VB User1 0

    Why are these features removed in preview 9? — Microsoft.VisualBasic.ApplicationServices, Microsoft.VisualBasic.Devices, Microsoft.VisualBasic.MyServices. — I’m worried because I frequently use Microsoft.VisualBasic with .NET Framework.

    • Kathleen DollardMicrosoft employee 0

      These classes have dependendies on WinForms.
      In .NET Core, we are splitting the Visual Basic runtime into a portion in CoreFx and a portion that depends on WinForms. As we’ve previously announced, WinForms support will not be in .NET Core 3.0. 
      We initially thought we could split these classes and included portions of these classes in CoreFx and earlier previews contained these classes. We realized this was a terrible idea – it relied heavily on reflection and would give runtime errors when WinForms was not availble. Thus, we removed all but one of the classes that depends on WinForms. We left Interaction because it contains IIf. 

      • VB User1 0

        Thank you for your response.
        Will these removed features be implemented someday?
        Where is ‘we’ve previously announced’ ?.

      • Dean Jackson 0

        Where was it previously announced ??

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