Question The type or namespace name 'Collections' does not exist in the namespace 'UnityEngine.UI'

Hi,
I trying upgrade my project from Unity 2019.4.7 to Unity 2019.4.32.
when Project in Version 2019.4.32,
I got compile error like this
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\CanvasUpdateRegistry.cs(3,22): error CS0234: The type or namespace name 'Collections' does not exist in the namespace 'UnityEngine.UI' (are you missing an assembly reference?)

I tried re-downloading Unity UI from Package manager or tried to restart unity,
the error still exists

Does anyone know what happened?
How can I fix this error. Q^Q

 

Editor.log
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\CanvasUpdateRegistry.cs(3,22): error CS0234: The type or namespace name 'Collections' does not exist in the namespace 'UnityEngine.UI' (are you missing an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\GraphicRebuildTracker.cs(3,22): error CS0234: The type or namespace name 'Collections' does not exist in the namespace 'UnityEngine.UI' (are you missing an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\GraphicRegistry.cs(2,22): error CS0234: The type or namespace name 'Collections' does not exist in the namespace 'UnityEngine.UI' (are you missing an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\CanvasUpdateRegistry.cs(86,26): error CS0246: The type or namespace name 'IndexedSet<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\CanvasUpdateRegistry.cs(87,26): error CS0246: The type or namespace name 'IndexedSet<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(17,75): error CS0246: The type or namespace name 'ILayoutElement' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\MaskableGraphic.cs(10,54): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\MaskableGraphic.cs(10,77): error CS0246: The type or namespace name 'IMaterialModifier' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\GraphicRebuildTracker.cs(13,16): error CS0246: The type or namespace name 'IndexedSet<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\GraphicRegistry.cs(13,45): error CS0246: The type or namespace name 'IndexedSet<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Graphic.cs(702,47): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(841,48): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(937,35): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\EventSystem\ExecuteEvents.cs(236,33): error CS0246: The type or namespace name 'ObjectPool<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(953,37): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(996,43): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(1074,34): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Mask.cs(19,60): error CS0246: The type or namespace name 'IMaterialModifier' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(1318,29): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(1329,29): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(1380,35): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\InputField.cs(26,9): error CS0246: The type or namespace name 'ILayoutElement' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(23,44): error CS0246: The type or namespace name 'IClipper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\MaskUtilities.cs(140,58): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RawImage.cs(132,48): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\ScrollRect.cs(18,159): error CS0246: The type or namespace name 'ILayoutElement' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\ScrollRect.cs(18,175): error CS0246: The type or namespace name 'ILayoutGroup' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(301,34): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(320,37): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(26,26): error CS0246: The type or namespace name 'RectangularVertexClipper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(35,25): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Text.cs(10,42): error CS0246: The type or namespace name 'ILayoutElement' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Graphic.cs(173,49): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Text.cs(641,48): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\InputField.cs(2618,36): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\InputField.cs(2710,40): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
-----CompilerOutput:-stderr----------
-----EndCompilerOutput---------------
- Finished compile Library/ScriptAssemblies/UnityEngine.TestRunner.dll in 1.536393 seconds
- Finished script compilation in 1.587601 seconds
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\CanvasUpdateRegistry.cs(3,22): error CS0234: The type or namespace name 'Collections' does not exist in the namespace 'UnityEngine.UI' (are you missing an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\GraphicRebuildTracker.cs(3,22): error CS0234: The type or namespace name 'Collections' does not exist in the namespace 'UnityEngine.UI' (are you missing an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\GraphicRegistry.cs(2,22): error CS0234: The type or namespace name 'Collections' does not exist in the namespace 'UnityEngine.UI' (are you missing an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\CanvasUpdateRegistry.cs(86,26): error CS0246: The type or namespace name 'IndexedSet<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\CanvasUpdateRegistry.cs(87,26): error CS0246: The type or namespace name 'IndexedSet<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(17,75): error CS0246: The type or namespace name 'ILayoutElement' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\MaskableGraphic.cs(10,54): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\MaskableGraphic.cs(10,77): error CS0246: The type or namespace name 'IMaterialModifier' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\GraphicRebuildTracker.cs(13,16): error CS0246: The type or namespace name 'IndexedSet<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\GraphicRegistry.cs(13,45): error CS0246: The type or namespace name 'IndexedSet<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Graphic.cs(702,47): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(841,48): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(937,35): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\EventSystem\ExecuteEvents.cs(236,33): error CS0246: The type or namespace name 'ObjectPool<>' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(953,37): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(996,43): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(1074,34): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Mask.cs(19,60): error CS0246: The type or namespace name 'IMaterialModifier' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(1318,29): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(1329,29): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Image.cs(1380,35): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\InputField.cs(26,9): error CS0246: The type or namespace name 'ILayoutElement' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(23,44): error CS0246: The type or namespace name 'IClipper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\MaskUtilities.cs(140,58): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RawImage.cs(132,48): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\ScrollRect.cs(18,159): error CS0246: The type or namespace name 'ILayoutElement' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\ScrollRect.cs(18,175): error CS0246: The type or namespace name 'ILayoutGroup' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(301,34): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(320,37): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(26,26): error CS0246: The type or namespace name 'RectangularVertexClipper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\RectMask2D.cs(35,25): error CS0246: The type or namespace name 'IClippable' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Text.cs(10,42): error CS0246: The type or namespace name 'ILayoutElement' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Graphic.cs(173,49): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\Text.cs(641,48): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\InputField.cs(2618,36): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)
Library\PackageCache\com.unity.ugui@1.0.0\Runtime\UI\Core\InputField.cs(2710,40): error CS0246: The type or namespace name 'VertexHelper' could not be found (are you missing a using directive or an assembly reference?)

 

Close Unity
Delete all CSproj files in the root of the project
Open Unity
Go to preferences -> External Tools
Make sure Visual Studio (VS) is selected for external script editor
Select Embedded, local, registry and built-in (others if you use them)
Click regenerate project files
Start VS/edit script
Should be fixed

 

Thank you for the advice~
I found the problem,
The reason is that the system blocked some of the downloaded packets.
Lead to incomplete ugui loading

 

Tanks