为什么 msbuild 15 不能识别 pack 目标，如果它可以很好地识别还原目标？

Question

所以我可以很好地恢复和构建：

C:\xyz\MyApp [master ↑1]> git clean -qdfx
C:\xyz\MyApp [master ↑1]> msbuild /t:restore
Microsoft (R) Build Engine version 15.8.169+g1ccb72aefa for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

Building the projects in this solution one at a time. To enable parallel build, please add the "/m" switch.
Build started 11/18/2018 8:24:37 PM.
Project "C:\xyz\MyApp\MyApp.sln" on node 1 (Restore target(s)).
ValidateSolutionConfiguration:
  Building solution configuration "Debug|Any CPU".
Restore:
  Restoring packages for C:\xyz\MyApp\MyApp\MyApp.csproj...
  Restoring packages for C:\xyz\MyApp\MyAppFileTool\MyAppFileTool.csproj...
  Restoring packages for C:\xyz\MyApp\MyAppHelper\MyAppHelper.csproj...
  Committing restore...
  Committing restore...
  Committing restore...
  Generating MSBuild file C:\xyz\MyApp\MyAppFileTool\obj\MyAppFileTool.csproj.nuget.g.props.
  Generating MSBuild file C:\xyz\MyApp\MyApp\obj\MyApp.csproj.nuget.g.props.
  Generating MSBuild file C:\xyz\MyApp\MyAppHelper\obj\MyAppHelper.csproj.nuget.g.props.
  Generating MSBuild file C:\xyz\MyApp\MyAppFileTool\obj\MyAppFileTool.csproj.nuget.g.targets.
  Generating MSBuild file C:\xyz\MyApp\MyApp\obj\MyApp.csproj.nuget.g.targets.
  Generating MSBuild file C:\xyz\MyApp\MyAppHelper\obj\MyAppHelper.csproj.nuget.g.targets.
  Writing lock file to disk. Path: C:\xyz\MyApp\MyApp\obj\project.assets.json
  Writing lock file to disk. Path: C:\xyz\MyApp\MyAppFileTool\obj\project.assets.json
  Writing lock file to disk. Path: C:\xyz\MyApp\MyAppHelper\obj\project.assets.json
  Restore completed in 367.2 ms for C:\xyz\MyApp\MyAppHelper\MyAppHelper.csproj.
  Restore completed in 367.46 ms for C:\xyz\MyApp\MyApp\MyApp.csproj.
  Restore completed in 367.02 ms for C:\xyz\MyApp\MyAppFileTool\MyAppFileTool.csproj.

  NuGet Config files used:
      C:\Users\myself\AppData\Roaming\NuGet\NuGet.Config
      C:\Program Files (x86)\NuGet\Config\Microsoft.VisualStudio.Offline.config

  Feeds used:
      https://api.nuget.org/v3/index.json
      C:\Program Files (x86)\Microsoft SDKs\NuGetPackages\
Done Building Project "C:\xyz\MyApp\MyApp.sln" (Restore target(s)).


Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:01.01
C:\xyz\MyApp [master ↑1]> msbuild /m /v:m
Microsoft (R) Build Engine version 15.8.169+g1ccb72aefa for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

  MyAppHelper -> C:\xyz\MyApp\MyAppHelper\bin\Debug\MyAppHelper.dll
  MyApp -> C:\xyz\MyApp\MyApp\bin\Debug\MyApp.exe
  MyAppFileTool -> C:\xyz\MyApp\MyAppFileTool\bin\Debug\MyAppFileTool.exe

因此，我希望 pack 目标也可以工作，但事实并非如此：

C:\xyz\MyApp [master ↑1]> msbuild /t:pack
Microsoft (R) Build Engine version 15.8.169+g1ccb72aefa for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

Building the projects in this solution one at a time. To enable parallel build, please add the "/m" switch.
Build started 11/18/2018 8:24:55 PM.
Project "C:\xyz\MyApp\MyApp.sln" on node 1 (pack target(s)).
ValidateSolutionConfiguration:
  Building solution configuration "Debug|Any CPU".
Project "C:\xyz\MyApp\MyApp.sln" (1) is building "C:\xyz\MyApp\MyAppFileTool\MyAppFileTool.csproj" (2) on node 1 (pack target(s)).
C:\xyz\MyApp\MyAppFileTool\MyAppFileTool.csproj : error MSB4057: The target "pack" does not exist in the project.
Done Building Project "C:\xyz\MyApp\MyAppFileTool\MyAppFileTool.csproj" (pack target(s)) -- FAILED.

Project "C:\xyz\MyApp\MyApp.sln" (1) is building "C:\xyz\MyApp\MyApp\MyApp.csproj" (3) on node 1 (pack target(s)).
C:\xyz\MyApp\MyApp\MyApp.csproj : error MSB4057: The target "pack" does not exist in the project.
Done Building Project "C:\xyz\MyApp\MyApp\MyApp.csproj" (pack target(s)) -- FAILED.

Project "C:\xyz\MyApp\MyApp.sln" (1) is building "C:\xyz\MyApp\MyAppHelper\MyAppHelper.csproj" (4) on node 1 (pack target(s)).
C:\xyz\MyApp\MyAppHelper\MyAppHelper.csproj : error MSB4057: The target "pack" does not exist in the project.
Done Building Project "C:\xyz\MyApp\MyAppHelper\MyAppHelper.csproj" (pack target(s)) -- FAILED.

Done Building Project "C:\xyz\MyApp\MyApp.sln" (pack target(s)) -- FAILED.


Build FAILED.

"C:\xyz\MyApp\MyApp.sln" (pack target) (1) ->
"C:\xyz\MyApp\MyAppFileTool\MyAppFileTool.csproj" (pack target) (2) ->
  C:\xyz\MyApp\MyAppFileTool\MyAppFileTool.csproj : error MSB4057: The target "pack" does not exist in the project.


"C:\xyz\MyApp\MyApp.sln" (pack target) (1) ->
"C:\xyz\MyApp\MyApp\MyApp.csproj" (pack target) (3) ->
  C:\xyz\MyApp\MyApp\MyApp.csproj : error MSB4057: The target "pack" does not exist in the project.


"C:\xyz\MyApp\MyApp.sln" (pack target) (1) ->
"C:\xyz\MyApp\MyAppHelper\MyAppHelper.csproj" (pack target) (4) ->
  C:\xyz\MyApp\MyAppHelper\MyAppHelper.csproj : error MSB4057: The target "pack" does not exist in the project.

    0 Warning(s)
    3 Error(s)

Time Elapsed 00:00:00.27
C:\xyz\MyApp [master ↑1]>

怎么了？

编辑 1

我刚刚创建了一个新的 .NET Standard 项目，restore 和 pack 都可以正常工作。有问题的解决方案是我在 Visual Studio 2017 的帮助下转换为使用 PackageReference 的 .NET Framework 4.7.2 解决方案。我没有手动执行任何操作。

Answer 1

我绝不是 MSBuild 专家，但我相信这比说 NuGet 与 MSBuild 集成要复杂得多。我不相信 MSBuild 15 有内置的 NuGet 知识，甚至是还原目标，这可以通过创建一个空的 MSBuild 项目文件<Project></Project> 来确认。运行msbuild /t:restore，看到错误信息说没有目标还原。

因此，还原目标实际上并未内置到 msbuild.exe 中，而是实际定义在您的项目正在使用的目标文件中。因此，为了定义一个打包目标，您需要导入一个不同的目标文件。

从不太理论、更实用的角度来看，“旧”样式的 csproj 文件（导入 Microsoft.Common.CSharp.targets 或类似文件的文件）没有定义打包目标，但新的 SDK 样式的项目可以.

因此，为了能够从 msbuild 打包，您需要迁移到 SDK 样式的项目。有些人有一种误解，认为您需要以 .NET Core 为目标才能使用 SDK 样式的项目，但事实并非如此。 SDK 风格的项目与 .NET Core 同时可用，而 .NET Core 项目需要 SDK 风格的项目，但您仍然可以以 .NET Framework 为目标。