OmniSharp返回“No Symbol Found”后功能部分失效问题求助

问题现象 #

• 启动VSCode后OmniSharp返回No Symbol Found错误
• C#智能提示仅识别部分关键词，日志频繁出现Received response for '某操作' but could not find request类报错
• 空白项目新脚本的void Update()中输入OnTriggerEnter2D时，提示The name 'OnTriggerEnter2D' does not exist in the current context [Assembly-CSharp]
• 此前功能正常，近期执行过迁移项目到副硬盘、安装GitHub、更新Unity和C#插件等操作

OmniSharp日志摘要 #

Starting OmniSharp server at 05/01/2023, 6:08:15 pm
    Target: d:\Unity Projects\2023-1-5\2023-1-5.sln

OmniSharp server started.
    Path: c:\Users\Alex\.vscode\extensions\ms-dotnettools.csharp-1.25.2-win32-x64\.omnisharp\1.39.2\OmniSharp.exe
    PID: 19916

[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: Visual Studio Build Tools 2022 17.4.33205.214 17.4.1 - "C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\MSBuild\Current\Bin"
[info]: OmniSharp.MSBuild.ProjectManager
        Successfully loaded project file 'd:\Unity Projects\2023-1-5\Assembly-CSharp.csproj'.
Received response for /v2/getcodeactions but could not find request.
[warn]: OmniSharp.Roslyn.CSharp.Services.Navigation.FindUsagesService
        No symbol found. File: d:\Unity Projects\2023-1-5\Assets\NewBehaviourScript.cs, Line: 15, Column: 13.
Received response for /quickinfo but could not find request.

已尝试的无效操作 #

• 重启电脑
• 重装Unity、VSCode及C#插件
• 重新生成Unity项目文件
• 重装VSCode
• 确认安装.NET框架和SDK

针对性解决方案 #

1. 强制OmniSharp使用Unity自带的MSBuild #

Unity 2021.3依赖.NET Framework 4.7.1，VS2022的MSBuild存在兼容性问题，需指定Unity内置的MSBuild路径：

• 打开VSCode设置（快捷键Ctrl+,）
• 搜索omnisharp.msbuild.path
• 输入Unity安装目录下的MSBuild路径，示例：D:\Unity\2021.3.16f1\Editor\Data\Tools\MSBuild\Current\Bin\MSBuild.exe
• 重启VSCode，等待OmniSharp重新加载

2. 禁用OmniSharp现代.NET支持 #

Unity基于传统.NET Framework，无需启用.NET Core/.NET 5+支持：

• 在VSCode设置中搜索omnisharp.useModernNet
• 将该选项设置为false
• 重启OmniSharp（命令面板执行OmniSharp: Restart OmniSharp）

3. 彻底清理OmniSharp缓存 #

缓存损坏可能导致请求匹配失败：

• 关闭VSCode
• 删除缓存目录：C:\Users\Alex\.omnisharp
• 重新打开项目，让OmniSharp重新生成缓存

4. 修复项目路径关联 #

迁移目录后项目文件路径可能失效：

• 打开Unity编辑器，进入Edit > Preferences > External Tools
• 确认External Script Editor选择的是Visual Studio Code
• 点击Regenerate project files，等待生成完成后重启VSCode

5. 确认.NET Framework 4.7.1开发包安装 #

确保安装的是**开发包（Developer Pack）**而非仅运行时：

• 打开控制面板程序和功能
• 查找.NET Framework 4.7.1 Developer Pack，若未安装则下载安装对应版本

内容的提问来源于stack exchange，提问作者JustAlex