The type or namespace name 'UI' does not exist in the namespace 'UnityEngine' HELP!

from Edit - preferences - external tools - choos visual studio open any c# file. then check all generate .csproj file , and click "Regenerate project files" button.

 

Hello, Everyone,

After days of torment, and trying all the suggestions listed here, we had still the problem of UnityEngine.UI is not defined.

How we resolve the problem is the following.

1) We export the entire project as a unitypackage.
2) We create the "new" unity project from Unity Hub.
3) We imported the unitypackage back in.
4) Build success.

Peace.

 

Hey I figure out another way around this. I tried a few of your ways mentioned above but nothing worked. When visual studio boots up it says that it loads UnityEngine.UI but I could not find it in "Project/Add Reference- Microsoft Visual Studio". I also regenerated the .csproj files multiple times doesn't change and also swapped / regenerated the Library files just wasted my time. I am using Unity (2020.3.23f1)

here what I did:

in visual studio solution it said that the both unityEngine.UI and UnitEditor.UI project weren't full loaded in "( )". Right click and reload them. Now your project can see .UI again. I am guess it fails to load correctly on start up of visual Studio. This is an after screenshot btw.

 

Hi folks,

I've the same very S***ty error and I still can't fix it with this article! The error is displayed 4 times in my Unity Editor 2022.1.0b3 on macOS Monterey 12.2. Please note that I've imported the asset ITG from here. I can code with C#, but only a little bit because I hadn't enough time to watch C# tutorials for Unity. Here's the source code of the scripts:

Script FPSCounter.cs:

Code (CSharp):

1. using System;
2. using UnityEngine;
3. using Unity.UI;
4.  
5. namespace UnityStandardAssets.Utility
6. {
7.     [RequireComponent(typeof (UI.Text))]
8.     public class FPSCounter : MonoBehaviour
9.     {
10.         const float fpsMeasurePeriod = 0.5f;
11.         private int m_FpsAccumulator = 0;
12.         private float m_FpsNextPeriod = 0;
13.         private int m_CurrentFps;
14.         const string display = "{0} FPS";
15.         private UI.Text m_GuiText;
16.  
17.  
18.         private void Start()
19.         {
20.             m_FpsNextPeriod = Time.realtimeSinceStartup + fpsMeasurePeriod;
21.             m_GuiText = GetComponent<UI.Text>();
22.         }
23.  
24.  
25.         private void Update()
26.         {
27.             // measure average frames per second
28.             m_FpsAccumulator++;
29.             if (Time.realtimeSinceStartup > m_FpsNextPeriod)
30.             {
31.                 m_CurrentFps = (int) (m_FpsAccumulator/fpsMeasurePeriod);
32.                 m_FpsAccumulator = 0;
33.                 m_FpsNextPeriod += fpsMeasurePeriod;
34.                 m_GuiText.text = string.Format(display, m_CurrentFps);
35.             }
36.         }
37.     }
38. }
39.  

Script ForcedReset.cs:

Code (CSharp):

1. using System;
2. using UnityEngine;
3. using UnityStandardAssets.CrossPlatformInput;
4. using Unity.UI;
5.  
6. [RequireComponent(typeof (UI.Texture))]
7. public class ForcedReset : MonoBehaviour
8. {
9.     private void Update()
10.     {
11.         // if we have forced a reset ...
12.         if (CrossPlatformInputManager.GetButtonDown("ResetObject"))
13.         {
14.             //... reload the scene
15.             Application.LoadLevelAsync(Application.loadedLevelName);
16.         }
17.     }
18. }
19.  

Script SimpleActivatorMenu:

Code (CSharp):

1. using System;
2. using UnityEngine;
3. using Unity.UI;
4.  
5. namespace UnityStandardAssets.Utility
6. {
7.     public class SimpleActivatorMenu : MonoBehaviour
8.     {
9.         // An incredibly simple menu which, when given references
10.         // to gameobjects in the scene
11.         public UI.Text camSwitchButton;
12.         public GameObject[] objects;
13.  
14.  
15.         private int m_CurrentActiveObject;
16.  
17.  
18.         private void OnEnable()
19.         {
20.             // active object starts from first in array
21.             m_CurrentActiveObject = 0;
22.             camSwitchButton.text = objects[m_CurrentActiveObject].name;
23.         }
24.  
25.  
26.         public void NextCamera()
27.         {
28.             int nextactiveobject = m_CurrentActiveObject + 1 >= objects.Length ? 0 : m_CurrentActiveObject + 1;
29.  
30.             for (int i = 0; i < objects.Length; i++)
31.             {
32.                 objects[i].SetActive(i == nextactiveobject);
33.             }
34.  
35.             m_CurrentActiveObject = nextactiveobject;
36.             camSwitchButton.text = objects[m_CurrentActiveObject].name;
37.         }
38.     }
39. }
40.  

If you can tell me, how to fix these very S***ty errors, I'm ging to be very happy because I very urgently need these assets! And sorry for the word S***ty, I wrote it here because all compiler errors in Unity (and this too) are annoying me because any error isn't good! In the attached screenshot there're the lines in the three scripts with the very S***ty compiler errors:


Sincerely yours,
Atten007

 

Merry Christmas! Please do keep your language professional or else Santa Claus won't bring you presents.

Remember, it's a computer. It has nothing but 1s and 0s in it, so cursing won't change that.

Some things to note:

UnityEngine.UI is now a package:

https://forum.unity.com/threads/where-did-the-ui-option-in-the-create-menu-go.1134796/#post-7290742

Annoying possible issue circa October 2021:

https://forum.unity.com/threads/unityeditor-ui-csproj-not-found.1177432/

This may help you with intellisense and possibly other Visual Studio integration problems:

Sometimes the fix is as simple as doing Assets -> Open C# Project from Unity. Other times it requires more.

https://forum.unity.com/threads/intellisense-not-working-with-visual-studio-fix.836599/

Also, try update the VSCode package inside of Unity: Window -> Package Manager -> Search for Visual Studio Code Editor -> Press the Update button

Also, this: https://forum.unity.com/threads/no-suggestions-in-vscode.955197/#post-6227874

 

This worked here, thank you so much!

 

This worked for me as well. Thanks!

 

Hey recently I am facing the same error have you found any solution? I am using the same version of unity

 

Found here:
https://issuetracker.unity3d.com/is...roduce-reference-errors-to-unityengine-dot-ui

For those who are facing this problem yet:

#1. Remove all .sln and .csproj files
#2. Make sure the "Generate all .csproj files." checkbox is checked on Preferences
#3. Reopen C# Project

This worked for me, hope help you as well

 

Deleting the library folder worked for me as well. Like others on this thread, I have a teammate developing on a Linux machine. Maybe this was the cause.

 

For me this often happens if I have had multiple instances of Unity open at the same time. The solution is usually very simple, close all Unity instances and open them again.

 

This is due to one issue. UnityUI.dll is present in the location of Library/ScriptAssemblies(library of your project).

If you will open your Assembly-CSharp.csproj ,search

<Reference Include="UnityEngine.UI">

if it is not present there add

For Mac Users

<Reference Include="UnityEngine.UI">
<HintPath>/Users/[Path to your current project]/Library/ScriptAssemblies/UnityEngine.UI.dll</HintPath>
</Reference>

For Window Users

<Reference Include="UnityEngine.UI">
<HintPath>Library\ScriptAssemblies\UnityEngine.UI.dll</HintPath>
</Reference>

 

For me, I didn't have to do step 2. I only needed to click Regenerate project files after I installed .NET sdk and Mono framework.

 

This one worked for me. Thankfully i didn't have to delete the library. Uncheck all but the top three yes. thank you

 

[Unity 2020.3.33f1, Windows]
I tried some of the fixes like rebuilding the project from both VS'19 and Unity Editor, but it didn't work. Tried deleting the Library folder from my project folder, and the namespace issue is fixed for me.

 

Thankx Bro this worked for me

 

I see this problem maybe from too long time ago. But I would like to share my solution if someone need it and the same case with me.

Basically, the problem happen right after I remove old version Admob and import new version and the problem show up. After doing many way to solve and the error still there. I do these simple step

1. Remove the new Admob version -> error gone
2. Import new Admob version again -> fixed

I am not sure why or maybe in my first import having some process not work. I believe it can be the same for other plugin/extension in import process. So just delete new one and import again

Hope it help

 

Hi Bro Solved the problem, very simple. Delete Unity Hub

 

This is a useful page of solutions to gotchas.
Perhaps it could be included into the main documentation somehow?
In my case, deleting the Library folder and then reloading the project (thereby rebuilding it) appeared to fix the problem - that was the first one from the suggestions above that I tried.
Perhaps some of these other suggestions would also have worked.

 

Yes, did anybody try just closing the editor and opening it again? I see everybody deleting folders before doing this. But the thing that fixed things might just be the closing and opening, not the removal of the Library folder or deleting the hub or standing on your head.

 

I was porting an old project to 2022.3.1f1 and after trying all the provided solutions above with no success, simply installing the Unity UI package from the Unity Registry solved my problem.