项目构建错误 - 与 NET Standard.Library 2.0.1 有关（我认为！）

Question

我在尝试构建我的项目时遇到了这个奇怪的错误：

Error: The reference to the built-in metadata "FileName" at position 1 is not allowed in this condition "'%(FileName)' != 'netstandard'".  C:\github\VS\API\VS.API.Public\VS.API.Public.csproj
 at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject(String errorSubCategoryResourceName, IElementLocation elementLocation, String resourceName, Object[] args)
 at Microsoft.Build.Evaluation.Parser.Parse(String expression, ParserOptions optionSettings, ElementLocation elementLocation)
 at Microsoft.Build.Evaluation.ConditionEvaluator.EvaluateConditionCollectingConditionedProperties[P,I](String condition, ParserOptions options, Expander`2 expander, ExpanderOptions expanderOptions, Dictionary`2 conditionedPropertiesTable, String evaluationDirectory, ElementLocation elementLocation, ILoggingService loggingServices, BuildEventContext buildEventContext, ProjectRootElementCache projectRootElementCache)
 at Microsoft.Build.Execution.ProjectInstance.EvaluateCondition(String condition)
 at JetBrains.Platform.MsBuild.TaskCommon.ProjectModel.Bindings.AddWildcardItemsFromXml(ProjectRootElement element, Boolean isImported, ProjectInstance projectInstance, List`1 items)
 at JetBrains.Platform.MsBuild.TaskCommon.ProjectModel.Bindings.BindWildcardItems(Project project, ProjectInstance projectInstance)
 at JetBrains.Platform.MsBuild.TaskCommon.ProjectModel.Bindings.Bind(Project project, ProjectInstance projectInstance, List`1 targetErrors, List`1 targetWarnings, Dictionary`2 resultsByTarget)
 at JetBrains.Platform.MsBuild.TaskCommon.ProjectModel.Bindings.Bind(Project project, ProjectInstance projectInstance)
 at JetBrains.Platform.MsBuild.TaskCommon.Build.BuildSessionHost.HandleSubmissionFinished(RdBuildRequest request, ProjectWithEvents projectWithEvents, Boolean succeeded, RdTask`1 rdTask)

我不知道这个错误是什么意思，也不知道从哪里开始。这是一个 Web API 项目，当我对项目进行重建时，它会出现在 Visual Studio 的构建结果 window 中。

错误提到了这种情况的问题：.csproj 文件中的 '%(FileName)' != 'netstandard'。但是在 .csproj 文件中搜索时不会出现这种情况。

如果我搜索解决方案文件夹中的所有文件，我可以在 C:\github\vs\packages\NETStandard.Library.2.0.1\build:

中找到它

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <NETStandardLibraryPackageVersion>2.0.1</NETStandardLibraryPackageVersion>
  </PropertyGroup>

  <ItemGroup Condition="'$(_NetStandardLibraryRefPath)' != ''">
    <Reference Include="$(_NetStandardLibraryRefPath)*.dll">
      <!-- Private = false to make these reference only -->
      <Private>false</Private>
      <!-- hide these from Assemblies view in Solution Explorer, they will be shown under packages -->
      <Visible>false</Visible>
      <Facade Condition="'%(FileName)' != 'netstandard'">true</Facade>
      <NuGetPackageId>NETStandard.Library</NuGetPackageId>
      <NuGetPackageVersion>$(NETStandardLibraryPackageVersion)</NuGetPackageVersion>
    </Reference>
    <ReferenceCopyLocalPaths Condition="'$(_NetStandardLibraryLibPath)' != ''" Include="$(_NetStandardLibraryLibPath)*.dll">
      <Private>false</Private>
      <Facade Condition="'%(FileName)' != 'netstandard'">true</Facade>
      <NuGetPackageId>NETStandard.Library</NuGetPackageId>
      <NuGetPackageVersion>$(NETStandardLibraryPackageVersion)</NuGetPackageVersion>
    </ReferenceCopyLocalPaths>
  </ItemGroup>
</Project>

但我对 .targets 文件的工作原理知之甚少，无法知道如何解决这个问题...通常它可以正常工作。

如果我尝试 google 这个错误，我也找不到任何相关结果。有人知道这里出了什么问题吗？

我正在使用 Visual Studio Professional 15.6.0。该项目针对.net462。

Answer 1

But I don't know enough about how .targets files work to know how to resolve this

根据 NuGet 文档 Creating native packages:

A package may also include targets and props files in \build that NuGet will automatically import into projects that consume the package.

这意味着 NuGet 会将适当的 .props 和 .targets 文件导入到项目中。因此，当您将包 NETStandard.Library.2.0.1 安装到项目中时，NETStandard.Library.targets 文件（位于该包的 \build 文件夹中）将被导入到项目文件中，卸载您的项目，编辑它，然后你会发现下面的代码：

 <Import Project="..\packages\NETStandard.Library.2.0.1\build\NETStandard.Library.targets" Condition="Exists('..\packages\NETStandard.Library.2.0.1\build\NETStandard.Library.targets')" />

现在，.targets 文件将用作项目文件。

和你想的一样，这个问题的原因应该和包NETStandard.Library.2.0.1有关。

根据 MSBuild 文档 MSBuild Batching：

Property functions may not appear within metadata values. For example,

%(Compile.FullPath.Substring(0,3))

is not allowed.

所以你会得到那个错误

the built-in metadata "FileName" at position 1 is not allowed in this condition "'%(FileName)' != 'netstandard'"

要解决此问题，您可以在自定义目标中指定 ItemGroup：

<Target Name="YourCustomName">    
  <ItemGroup Condition="'$(_NetStandardLibraryRefPath)' != ''">
    <Reference Include="$(_NetStandardLibraryRefPath)*.dll">
...
    </Reference>
    <ReferenceCopyLocalPaths Condition="'$(_NetStandardLibraryLibPath)' != ''" Include="$(_NetStandardLibraryLibPath)*.dll">
...
  </ItemGroup>       
<Message Text="@(Reference)"/>
</Target>

来源：How do you filter an ItemGroup?

或者，您可以创建一个属性来存储此自定义元数据的值：

<PropertyGroup>
   <FimeName>%(FileName)</FimeName>
</Pro‌pertyGroup>

<ItemGroup>
   ...
      <Facade Condition="'$(FileName)' != 'netstandard'">true</Facade>
    ...
</ItemGroup>

来源：Using metadata in conditions

此外，如果你能确定你没有使用那个.targets文件，你可以尝试删除项目文件中的<Import Project="..\packages\NETStandard.Library.2.0.1\build\NETStandard.Library.targets" ... />。

项目构建错误 - 与 NET Standard.Library 2.0.1 有关（我认为！）

Project Build Error - Something to do with NETStandard.Library2.0.1 (I think!)

msbuild

csproj

visual-studio

.net-standard