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Fixed in 2019.3.X

Fixed in 2019.2.X



Found in




Issue ID




UnityEngine.UI reference is missing in Assembly Definition Assemblies and Plugins



To reproduce:

1. Download attached “" project and open in Unity
2. Open Console window

Expected results: There is no Error
Actual results: There is Error:

"Assets/AsmDef/Test.cs(1,19): error CS0234: The type or namespace name 'UI' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)"

- This issue appears both on Windows and macOS
- Notice how UnityEngine.UI resolves properly with a normal Script (Assets/Test.cs)
- Notice how UnityEngine.UI fails to resolve in the Script placed under an Assembly Definition (Assets/AsmDef/Test.cs)

Reproduced on Unity 2019.2.0a5, 2019.2.0b2 and 2019.3.0a3
Not reproduced on Unity 2019.2.0a4
Regression on Unity 2019.2.0a5

Comments (13)

  1. 669741ab71fdb5367626274baf5bc606?d=mm


    Aug 29, 2020 19:48

    I am still having this issue with 2019.4.1f1
    No 3rd party packages are installed, just the new Input System, and URP.

    I was able to fix it with Edit > Preferences.. > External Tools and regenerating .csproj files for everything.
    It's only ever UnityEngine.UI that gets lost.

  2. 6b773cce473423370d67835cd20fc667?d=mm


    Apr 05, 2020 16:59

    Impressionante como este tipo de problema é recorrente na Unity! As vezes dá vontade até mesmo de desistir! O problema continua nas versões mais novas! Qual é o problema de vocês?

  3. 70ce7b009114a427a051ba3b70c55c90?d=mm


    Apr 02, 2020 14:15

    I am still experiencing this error upgrading to 2019.3.7f1

  4. 673101a86c300d84324927f46c4b5b04?d=mm


    Jan 29, 2020 00:22

    ...the issue re-appears always when I create a new C#-script inside one of my project folders. Could be fixed the same way (downgrade to VSCode package 1.1.3, close Unity, open it again and upgrade to 1.1.4)

  5. 673101a86c300d84324927f46c4b5b04?d=mm


    Jan 29, 2020 00:10

    upgraded to 2019.3.0f6 and had the same issue with VSCode. Fixed it by downgrading the VSCode package to 1.1.3 and then back to 1.1.4.

  6. 6abdb60131b63dd460b3a6629427ad55?d=mm


    Jan 08, 2020 01:58

    Still have the same error in 2019.3.0f3

  7. 3bb3f461f93ea3a3b40a29d18500a8dc?d=mm


    Jun 25, 2019 22:06

    This appears to be fixed in 2019.3.0a6

  8. E72bf0515f288873b012f7b14769f125?d=mm


    Jun 19, 2019 18:39

    This error also appears on 2019.3.0a3 when installing graphy !

  9. 9f98cf164ab8ae9c2a496301c19b4c71?d=mm


    Jun 07, 2019 05:19

    I am still encountering the issue in version 2019.3.0a5.

    Looking at the files:

    In my .csproj file the old UI dll (from 2019.2.0a11) entry would look like this:

    <Reference Include="UnityEngine.UI">
    <HintPath>C:/Program Files/Unity/Hub/Editor/2019.2.0a11/Editor/Data/UnityExtensions/Unity/GUISystem/UnityEngine.UI.dll</HintPath>

    If we go look into the same path in the 2019.3.0a5 path, the GUISystem folder under .../Editor/Data/UnityExtensions/Unity/ is missing.

    If I copy it manually from the old version (2019.2.0a11) into the new (2019.3.0a5) and restart Unity I get these kind of errors:

    Library\PackageCache\com.unity.textmeshpro@2.0.1\Scripts\Runtime\TMP_Dropdown.cs(170,16): error CS0433: The type 'Image' exists in both 'Unity.ugui, Version=, Culture=neutral, PublicKeyToken=null' and 'UnityEngine.UI, Version=, Culture=neutral, PublicKeyToken=null'

    Got a similar errors with the analytics. So I uninstalled the the '' and 'com.unity.textmeshpro' and now the project builds. But the UI is not showing. Nothing on the UI canvas.

    Had to revert back to 2019.2.0a11.

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