我有一个 nuget/docker 构建问题，我已经花了几天时间进行调试并且没有想法：你知道我为什么会收到以下错误吗？
问题在于一个 asp.net 核心解决方案（其他非常相似的不受影响）：虽然我可以使用 docker compose 文件在 Visual Studio 2019 中构建受影响的解决方案，但它无法使用 dockerfile 和 docker build 命令无法运行。
如果我通过在命令提示符下执行如下构建来运行 dockerfile：
docker build -f MStoreBosGateway/MStoreBosGatewayApi/Dockerfile --pull --no-cache -t mstorebosgateway:0.041 .
然后我收到以下错误：
Step 11/26 : RUN dotnet restore "MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj"
> ---> Running in 30819cb5db4f
> /usr/share/dotnet/sdk/2.2.402/NuGet.targets(123,5): error : An error
> occurred while retrieving package metadata for
> 'System.Text.Encodings.Web.4.5.0' from source
> '/usr/share/dotnet/sdk/NuGetFallbackFolder'.
> [/src/MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj]
> /usr/share/dotnet/sdk/2.2.402/NuGet.targets(123,5): error : Root
> element is missing.
> [/src/MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj]
> The command '/bin/sh -c dotnet restore
> "MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj"'
> returned a non-zero code: 1
我在 dockerfile 的每一行之后都放置了 RUN echo 命令，所以看起来是 dotnet restore 导致了这个问题。如果我自己运行 dotnet restore 命令，它运行正常。
为了解决这个问题，我做了很多事情，例如
- - 从此解决方案和项目中删除了 obj 和 bin 文件夹，
- -卸载并重新安装nuget，
- -删除了nuget缓存以强制重新下载包，
- -卸载并重新安装 dotnet core sdks，
- -从项目文件中删除了错误消息中提到的包（'System.Text.Encodings.Web.4.5.0）（这不会导致任何错误，所以无论如何肯定是多余的）。这并没有影响这个错误，它恢复了这个包，所以必须有别的东西说要使用这个包，或者可能系统包都默认包含在内。
我的同事可以构建这个项目，并给我发了一份他可以构建的副本；我在构建他的副本时遇到了同样的问题，所以假设它是项目外部的东西。
如果我在 docker 文件中的 dotnet restore 命令中添加“--verbosity detail”，我已在输出下方添加。
GET https://api.nuget.org/v3-flatcontainer/microsoft.extensions.dependencyinjection.abstractions/index.json
OK https://api.nuget.org/v3-flatcontainer/aspnet.security.oauth.validation/index.json 342ms
GET https://api.nuget.org/v3-flatcontainer/aspnet.security.oauth.validation/2.0.0/aspnet.security.oauth.validation.2.0.0.nupkg
OK https://api.nuget.org/v3-flatcontainer/aspnet.security.oauth.validation/2.0.0/aspnet.security.oauth.validation.2.0.0.nupkg 52ms
GET https://api.nuget.org/v3-flatcontainer/microsoft.aspnetcore.authentication/index.json
GET https://api.nuget.org/v3-flatcontainer/newtonsoft.json/10.0.2/newtonsoft.json.10.0.2.nupkg
1>/usr/share/dotnet/sdk/2.2.402/NuGet.targets(123,5): error : An error occurred while retrieving package metadata for 'System.Text.Encodings.Web.4.5.0' from source '/usr/share/dotnet/sdk/NuGetFallbackFolder'. [/src/MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj]
/usr/share/dotnet/sdk/2.2.402/NuGet.targets(123,5): error : Root element is missing. [/src/MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj]
OK https://api.nuget.org/v3-flatcontainer/swashbuckle.aspnetcore.swaggergen/index.json 156ms
GET https://api.nuget.org/v3-flatcontainer/swashbuckle.aspnetcore.swaggergen/4.0.1/swashbuckle.aspnetcore.swaggergen.4.0.1.nupkg
OK https://api.nuget.org/v3-flatcontainer/swashbuckle.aspnetcore.swaggerui/index.json 160ms
GET https://api.nuget.org/v3-flatcontainer/swashbuckle.aspnetcore.swaggerui/4.0.1/swashbuckle.aspnetcore.swaggerui.4.0.1.nupkg
OK https://api.nuget.org/v3-flatcontainer/automapper/index.json 155ms
GET https://api.nuget.org/v3-flatcontainer/automapper/8.0.0/automapper.8.0.0.nupkg
OK https://api.nuget.org/v3-flatcontainer/swashbuckle.aspnetcore.swaggergen/4.0.1/swashbuckle.aspnetcore.swaggergen.4.0.1.nupkg 44ms
OK https://api.nuget.org/v3-flatcontainer/swashbuckle.aspnetcore.swaggerui/4.0.1/swashbuckle.aspnetcore.swaggerui.4.0.1.nupkg 49ms
GET https://api.nuget.org/v3-flatcontainer/microsoft.aspnetcore.mvc.apiexplorer/index.json
GET https://api.nuget.org/v3-flatcontainer/microsoft.aspnetcore.mvc.core/index.json
GET https://api.nuget.org/v3-flatcontainer/microsoft.aspnetcore.mvc.dataannotations/index.json
NuGet.Protocol.Core.Types.FatalProtocolException: An error occurred while retrieving package metadata for 'System.Text.Encodings.Web.4.5.0' from source '/usr/share/dotnet/sdk/NuGetFallbackFolder'. ---> NuGet.Packaging.Core.PackagingException: An error occurred while retrieving package metadata for 'System.Text.Encodings.Web.4.5.0' from source '/usr/share/dotnet/sdk/NuGetFallbackFolder'. ---> System.Xml.XmlException: Root element is missing.
at System.Xml.XmlTextReaderImpl.Throw(Exception e)
at System.Xml.XmlTextReaderImpl.ParseDocumentContent()
at System.Xml.XmlTextReaderImpl.Read()
at System.Xml.Linq.XDocument.Load(XmlReader reader, LoadOptions options)
at NuGet.Packaging.Core.NuspecCoreReaderBase.LoadXml(Stream stream, Boolean leaveStreamOpen)
at NuGet.Packaging.Core.NuspecCoreReaderBase..ctor(Stream stream, Boolean leaveStreamOpen)
at NuGet.Packaging.NuspecReader..ctor(Stream stream)
at NuGet.Protocol.LocalPackageFileCache.GetNuspec(String manifestPath, String expandedPath)
at NuGet.Protocol.LocalPackageFileCache.<>c__DisplayClass6_1.<GetOrAddNuspec>b__1()
at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode)
at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor)
at System.Lazy`1.CreateValue()
at NuGet.Protocol.LocalV3FindPackageByIdResource.ProcessNuspecReader[T](String id, NuGetVersion version, Func`2 process)
--- End of inner exception stack trace ---
--- End of inner exception stack trace ---
at NuGet.Protocol.LocalV3FindPackageByIdResource.ProcessNuspecReader[T](String id, NuGetVersion version, Func`2 process)
at NuGet.Protocol.LocalV3FindPackageByIdResource.GetDependencyInfoAsync(String id, NuGetVersion version, SourceCacheContext cacheContext, ILogger logger, CancellationToken cancellationToken)
at NuGet.Commands.SourceRepositoryDependencyProvider.GetDependenciesCoreAsync(LibraryIdentity match, NuGetFramework targetFramework, SourceCacheContext cacheContext, ILogger logger, CancellationToken cancellationToken)
at NuGet.Commands.SourceRepositoryDependencyProvider.<>c__DisplayClass21_0.<<GetDependenciesAsync>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at NuGet.Commands.SourceRepositoryDependencyProvider.GetDependenciesAsync(LibraryIdentity libraryIdentity, NuGetFramework targetFramework, SourceCacheContext cacheContext, ILogger logger, CancellationToken cancellationToken)
at NuGet.DependencyResolver.ResolverUtility.CreateGraphItemAsync(RemoteMatch match, NuGetFramework framework, SourceCacheContext cacheContext, ILogger logger, CancellationToken cancellationToken)
at NuGet.DependencyResolver.ResolverUtility.FindLibraryEntryAsync(LibraryRange libraryRange, NuGetFramework framework, String runtimeIdentifier, RemoteWalkContext context, CancellationToken cancellationToken)
at NuGet.DependencyResolver.RemoteDependencyWalker.CreateGraphNode(LibraryRange libraryRange, NuGetFramework framework, String runtimeName, RuntimeGraph runtimeGraph, Func`2 predicate, GraphEdge`1 outerEdge)
at NuGet.DependencyResolver.RemoteDependencyWalker.CreateGraphNode(LibraryRange libraryRange, NuGetFramework framework, String runtimeName, RuntimeGraph runtimeGraph, Func`2 predicate, GraphEdge`1 outerEdge)
at NuGet.DependencyResolver.RemoteDependencyWalker.CreateGraphNode(LibraryRange libraryRange, NuGetFramework framework, String runtimeName, RuntimeGraph runtimeGraph, Func`2 predicate, GraphEdge`1 outerEdge)
at NuGet.DependencyResolver.RemoteDependencyWalker.CreateGraphNode(LibraryRange libraryRange, NuGetFramework framework, String runtimeName, RuntimeGraph runtimeGraph, Func`2 predicate, GraphEdge`1 outerEdge)
at NuGet.DependencyResolver.RemoteDependencyWalker.CreateGraphNode(LibraryRange libraryRange, NuGetFramework framework, String runtimeName, RuntimeGraph runtimeGraph, Func`2 predicate, GraphEdge`1 outerEdge)
at NuGet.DependencyResolver.RemoteDependencyWalker.CreateGraphNode(LibraryRange libraryRange, NuGetFramework framework, String runtimeName, RuntimeGraph runtimeGraph, Func`2 predicate, GraphEdge`1 outerEdge)
at NuGet.DependencyResolver.RemoteDependencyWalker.CreateGraphNode(LibraryRange libraryRange, NuGetFramework framework, String runtimeName, RuntimeGraph runtimeGraph, Func`2 predicate, GraphEdge`1 outerEdge)
at NuGet.Commands.ProjectRestoreCommand.WalkDependenciesAsync(LibraryRange projectRange, NuGetFramework framework, String runtimeIdentifier, RuntimeGraph runtimeGraph, RemoteDependencyWalker walker, RemoteWalkContext context, CancellationToken token)
at NuGet.Commands.ProjectRestoreCommand.TryRestoreAsync(LibraryRange projectRange, IEnumerable`1 frameworkRuntimePairs, NuGetv3LocalRepository userPackageFolder, IReadOnlyList`1 fallbackPackageFolders, RemoteDependencyWalker remoteWalker, RemoteWalkContext context, Boolean forceRuntimeGraphCreation, CancellationToken token, TelemetryActivity telemetryActivity)
at NuGet.Commands.RestoreCommand.ExecuteRestoreAsync(NuGetv3LocalRepository userPackageFolder, IReadOnlyList`1 fallbackPackageFolders, RemoteWalkContext context, CancellationToken token, TelemetryActivity telemetryActivity)
at NuGet.Commands.RestoreCommand.ExecuteAsync(CancellationToken token)
at NuGet.Commands.RestoreRunner.ExecuteAsync(RestoreSummaryRequest summaryRequest, CancellationToken token)
at NuGet.Commands.RestoreRunner.ExecuteAndCommitAsync(RestoreSummaryRequest summaryRequest, CancellationToken token)
at NuGet.Commands.RestoreRunner.CompleteTaskAsync(List`1 restoreTasks)
at NuGet.Commands.RestoreRunner.RunAsync(IEnumerable`1 restoreRequests, RestoreArgs restoreContext, CancellationToken token)
at NuGet.Commands.RestoreRunner.RunAsync(RestoreArgs restoreContext, CancellationToken token)
at NuGet.Build.Tasks.RestoreTask.ExecuteAsync(ILogger log)
Done executing task "RestoreTask" -- FAILED.
1>Done building target "Restore" in project "MStoreBOSGatewayApi.csproj" -- FAILED.
1>Done Building Project "/src/MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj" (Restore target(s)) -- FAILED.
Build FAILED.
"/src/MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj" (Restore target) (1) ->
(Restore target) ->
/usr/share/dotnet/sdk/2.2.402/NuGet.targets(123,5): error : An error occurred while retrieving package metadata for 'System.Text.Encodings.Web.4.5.0' from source '/usr/share/dotnet/sdk/NuGetFallbackFolder'. [/src/MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj]
/usr/share/dotnet/sdk/2.2.402/NuGet.targets(123,5): error : Root element is missing. [/src/MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj]
0 Warning(s)
1 Error(s)
Time Elapsed 00:00:04.70
The command '/bin/sh -c dotnet restore "MStoreBOSGateway/MStoreBOSGatewayApi/MStoreBOSGatewayApi.csproj" --verbosity detailed' returned a non-zero code: 1
C:\Applications\VB2017Apps\MStoreBOSGateway>