尝试在 Visual Studio 2017 中为 Unity 2D 编译 c# 脚本时出现“未定义或导入预定义类型 System.Void”错误

Question

I'm trying to learn creating 2D videogames with Unity but i can't compile my script for CharacterMovement because of several errors. Even creating a new empty script, the compiler says that "Predefined type System.Void is not defined or imported" and i couldn't find online a way to fix this.

This is the empty script :

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class MyPlayerMovement : MonoBehaviour
{
    // Start is called before the first frame update
    void Start()
    {

    }

    // Update is called once per frame
    void Update()
    {

    }
}

And this is the script i'm trying to compile :

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerMovement : MonoBehaviour {

    public CharacterController2D controller;
    public Animator animator;

    public float runSpeed = 40f;

    float horizontalMove = 0f;
    bool jump = false;
    bool crouch = false;

    // Update is called once per frame
    void Update () {

        horizontalMove = Input.GetAxisRaw("Horizontal") * runSpeed;

        animator.SetFloat("Speed", Mathf.Abs(horizontalMove));

        if(horizontalMove == 0)
        {
            animator.SetBool("Jumping", false);
        }

        if (Input.GetButtonDown("Jump"))
        {
            jump = true;
            animator.SetBool("Jumping", true);
        }

        if (Input.GetButtonDown("Crouch"))
        {
            crouch = true;
            animator.SetBool("Crouching", true);
        } else if (Input.GetButtonUp("Crouch"))
        {
            crouch = false;
            animator.SetBool("Crouching", false);
        }

    }

    void FixedUpdate ()
    {
        // Move our character
        controller.Move(horizontalMove * Time.fixedDeltaTime, crouch, jump);
        jump = false;
    }
}

(On my script i get about 60 errors all similar)

Answer 1

将File->BuildSettings->playersettings-api 兼容级别中的选项更改为 .Net 4X

Answer 2

Another possible solution for those stumbling across this in the future: Go to Edit->Preferences->External Tools->Regenerate project files to bring back the original CS Project & VS solution files.

That was the only option that worked after trying other common answers like changing API compatibility, upgrading VS, or deleting the project obj folder. I think it broke like that due to me trying to clean out the solution manually and Unity ended up corrupting some packages after I attempted to delete them. So unfortunately it seems you will get this error if you try to do that.

Answer 3

This happened when I tried to install Microsoft.Toolkit.Uwp.Notification using Install-Package Microsoft.Toolkit.Uwp.Notifications -Version 7.1.2 .

Once I do this, I notice a new config file is added to my solution explorer. I have to delete this to fix the error.