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Packages fail to compile and show Package Manager because of missing .NET Core prerequisites



How to reproduce:
1. Open a new project with 2018.2 version
2. Open the same project with 2018.3.0f2
3. Try to open the Package Manager Window

Expected result: Package Manager is under Window tab
Actual result: Package Manager does not exist under Window tab

Reproduced with: 2018.3.0f2

If you look in the editor logs, you'll notice this error message for all packages:

Failed to load the dll from [?P], HRESULT: 0x80070057
The library hostfxr.dll was found, but loading it from C:\Program Files\Unity Editors\2018.3.0f2\Editor\Data\Tools\Roslyn\hostfxr.dll failed
- Installing .NET Core prerequisites might help resolve this problem.

Comments (4)

  1. Joyedele

    Aug 18, 2021 19:36

    I went to the link but it is telling me that the download is no longer available.
    What should i do?

  2. Charles_Beauchemin

    Apr 12, 2019 18:25

    @DR-SEUSS: The Package Manager UI was introduced in 2018.1. It will never appear on 5.6.

  3. Dr-Seuss

    Mar 13, 2019 05:11

    I have this problem in unity version 5.6.3p2, which is currently the most up-to date version of unity. I have reinstalled unity, as well as installing Visual studio with the .net cross-platform development framework. I also updated the .net core SDK to 2.2, and still the package manager does not appear, in either pre-existing projects, or a new test project I created in this version of unity.

  4. mkderoy

    Jan 15, 2019 15:48

    If you experience this error make sure you have the following windows update installed

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