使用Vs2019,发现新创建的代码,也无法正常编译,
尝试过用visual自带的修复功能;去官网升级Nuget;甚至卸载Nuget;也无法解决.

详细报错内容如下

严重性	代码	说明	项目	文件	行	禁止显示状态
错误	MSB4018	“ResolvePackageAssets”任务意外失败。
NuGet.Packaging.Core.PackagingException: **Unable to find fallback package folder 'D:\Microsoft\Xamarin\NuGet\'.**在 NuGet.Packaging.FallbackPackagePathResolver..ctor(String userPackageFolder, IEnumerable`1 fallbackPackageFolders)在 Microsoft.NET.Build.Tasks.NuGetPackageResolver.CreateResolver(IEnumerable`1 packageFolders)在 Microsoft.NET.Build.Tasks.NuGetPackageResolver.CreateResolver(LockFile lockFile)在 Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheWriter..ctor(ResolvePackageAssets task)在 Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheReader.CreateReaderFromDisk(ResolvePackageAssets task, Byte[] settingsHash)在 Microsoft.NET.Build.Tasks.ResolvePackageAssets.CacheReader..ctor(ResolvePackageAssets task)在 Microsoft.NET.Build.Tasks.ResolvePackageAssets.ReadItemGroups()在 Microsoft.NET.Build.Tasks.ResolvePackageAssets.ExecuteCore()在 Microsoft.NET.Build.Tasks.TaskBase.Execute()在 Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()在 Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext()	DealExcel	C:\Program Files\dotnet\sdk\5.0.411\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets	241

查询若干方法后,发现解决方案就藏在第二排提示中
Unable to find fallback package folder ‘D:\Microsoft\Xamarin\NuGet’.**

新建一个空目录 folder ‘D:\Microsoft\Xamarin\NuGet’.
(把自己的visual报错复制出来,看提示路径在哪里,就在哪里建)

建好之后,问题就解决了

问题原因:之前以为D盘里面没有放编译相关程序,为了省空间,就全部手贱删掉,哪会知道有这种事情