Unity type or namespace name 'InputSystem' does not exist in the namespace 'UnityEngine'

The issue is that the required .csproj files (VSCode needs them to understand the available libraries) for the new package were not auto-generated when you installed the new package (it didn't happen for me either, maybe it is intentionally manual).

Go to Edit -> Preferences... and then click on External Tools. You need to tick the box to Generate .csproj files for: Registry packages (and any other ones you might want) and then click on Regenerate project files.

That should generate whatever is needed for VSCode to recognize the new package - you shouldn't even need to restart it.

There's multiple reasons for this issue

I had an existing Assembly Definition that needed an Assembly Definition Reference to Unity.InputSystem

I added an Assembly Definition Reference to Unity.InputSystem in the inspector for "Scripts"

Rebuild had 0 errors.

You need to install the package. Go to Windows / Package Manager. Search Input system and press install confirm to restart and replace the old input system.

Select your Input Action Asset, and turn on Generate C# Class from the inspector window and click on apply to generate a C# script file.

I had the same issue (Mac 10.15.17 with Unity 2019.3.151f1 personal) but the above didn't work 100% for me. Here was my solution:

First, I ensured that I installed the InputSystem package via the package manager. Window > Package Manager. Search for it and you should be able to install 1.0.2 which is the newest as of this post.

From there, I ensured that VS code was setup correctly. I when to Unity > Preferences > External Editor and ensured that VS code was the correct editor. I then selected Regenerate project files.

Lastly, on the script I was using, I included it in the top of the file like so:

using UnityEngine;
using UnityEngine.InputSystem;

If you get errors when Unity is trying to resolve the dependencies for the new Input System.Follow these steps and it should work: Regenerating your project only works, if you have the Input System actually installed.

1. Install Input System (Windows > Package Manager)

2. Set your project to new Input System (Project Settings > Player > Input System)

3. Regenerate Project Files

Like other answers suggested, try regenerating your project files. This will only work, if the previous steps were succesful.

close the Unity and VB, remove these files from the project folder *.sln *.csproj , run unity then click Assets -> open C# project

I did all the above and still had the problem. What finally, helped me was:

Changing VS Code package to 1.2.3. You can do that by going to:

Packages/Manifest.json

finding:

"com.unity.ide.vscode"

and changing version from "1.2.4" to "1.2.3"

The original solution was posted by user Cartina: https://forum.unity.com/threads/cannot-find-unityengine-inputsystem.807645/

I came across the same issue, and solved it. so, leaving a note here.

my case

In my case, after installing the new InputSystem package by Package Manger on Unity Editor, and then restarting Unity Editor following the appeared dialog, I could see Input System under Packages folder on Project view. However, any reference to namespece UnityEngine.InputSystem got errors.

What I found that Unity.InputSystem.dll didn't exist under [Project Dir]/Library/ScriptAssemblies/Unity.InputSystem.dll, which is what the Unity project refers to. This path can be found in Assembly-CSharp.csproj, placed right under Unity project directory.

Actually, it was not only for Input System package but also the same for all the other packages I uses. [Project Dir]/Library/ScriptAssemblies only had 2 files, Assembly-CSharp.dll and Assembly-CSharp.pdb, although this directory should hold dll files from all the installed packages.

solution

My solution was simple.

1. delete Assembly-CSharp.csproj file ( to be regenerated at some stage )
2. close Unity Editor
3. close Unity Hub
4. open Unity Hub
5. open Unity Editor

At the last step, before Unity Editor fully waked up, I could see all the package dll files are loaded to [Project Dir]/Library/ScriptAssemblies directory.

I'm not so sure whether csproj file delete and Unity Hub restart was necessary, but this is what I did, which recovered my broken project.

my environment

• Unity 2019.4.14f1
• macOS 10.15.7
• Visual Studio 8.8.4

In my case (Windows, Unity 2019.4 15f1, Visual Studio Code 1.53.0, Input System 1.0.2) Setting the Architecture of the project to x86_64 helped.

File-> Build Settings -> Plattform (PC, MAC & Linux Standalone)

I'm not sure though if this could even effect VS Code or if I did anything else in between to resolve this.

if you wanna Using Something Like inputField Or Etc. you can do it by add

using UnityEngine.UI;

In my case I was creating my Script in a third-party folder (Mirror). As soon as I moved it to my Scripts folder it worked.

Solution:
Go to Edit -> Preferences... and then click on External Tools. Remove the tick from the box for: Registry packages (and any other ones you might want) and then click on Regenerate project files.
I don't know why but it worked for me (no need to restart VS Code)
Image of the steps
Environment:
Unity version: 2020.2.7f1
VS Code version: 1.61.2
Input System Package version: 1.2.4