围绕非托管DLL的C#包装器库要求在构建过程中非托管DLL位于同一目录中

通常，当使用PInvoke引用封装了非托管DLL的托管DLL时，必须分别引用这两个DLL-托管的csproj中的托管DLL作为标准<Reference/>，而非托管的DLL链接为链接的<content/>(如概述) 此处).但是，我最近遇到了一个托管包装器库，它不仅在构建过程中自动复制非托管DLL，而且在同一目录中不存在非托管DLL时，实际上会产生一个构建错误！这是 Microsoft.Z3库，该库具有托管的DLL(Microsoft.Z3.dll)用PInvoke包装非托管DLL(libz3.dll)，以便可以在C#中使用该库.

Usually when referencing a managed DLL that wraps an unmanaged DLL with PInvoke, you have to reference those two DLLs separately - the managed one as a standard <Reference/> in your csproj and the unmanaged one as linked <content/> (as outlined here). However, I recently came across a managed wrapper library which not only auto-copies the unmanaged DLL along with it during the build, but actually produces a build error when the unmanaged DLL is not present in the same directory! This is the Microsoft.Z3 library, which has a managed DLL (Microsoft.Z3.dll) wrapping an unmanaged DLL (libz3.dll) with PInvoke so you can use the library in C#.

如果将两个Z3 DLL放在一个目录中，仅引用Microsoft.Z3.dll，然后使用msbuild编译项目，则将在输出目录中获得这两个DLL，而根本不引用libz3.dll！在msbuild /verbosity:diag产生的输出中，我看到以下对libz3.dll的引用:

If you put the two Z3 DLLs together in a directory, referencing only Microsoft.Z3.dll, then compile your project with msbuild, you'll get both DLLs in the output directory without referencing libz3.dll at all! Looking in the output produced by msbuild /verbosity:diag, I see the following references to libz3.dll:

Primary reference "Microsoft.Z3, Version=4.7.1.0, Culture=neutral, PublicKeyToken=9c8d792caae602a2". (TaskId:9)
      Resolved file path is "C:\Users\ahelwer\source\test\Framework\lib\z3\Microsoft.Z3.dll". (TaskId:9)
      Reference found at search path location "{HintPathFromItem}". (TaskId:9)
      Found embedded scatter file "libz3.dll". (TaskId:9)
      The ImageRuntimeVersion for this reference is "v4.0.30319". (TaskId:9)

...

Output Item(s): 
      _ReferenceScatterPaths=
          C:\Users\ahelwer\source\test\Framework\lib\z3\libz3.dll
                  CopyLocal=true
                  FusionName=
                  HintPath=lib\z3\Microsoft.Z3.dll
                  OriginalItemSpec=C:\Users\ahelwer\source\test\Framework\lib\z3\Microsoft.Z3.dll
                  ResolvedFrom={HintPathFromItem}
                  Version=4.7.1.0 (TaskId:9)

以某种方式导致它被复制:

Which somehow leads to it being copied:

Task "Copy" (TaskId:22)
  Task Parameter:
      SourceFiles=
          C:\Users\ahelwer\source\test\Framework\lib\z3\Microsoft.Z3.dll
                  CopyLocal=true
                  FusionName=Microsoft.Z3, Version=4.7.1.0, Culture=neutral, PublicKeyToken=9c8d792caae602a2
                  HintPath=lib\z3\Microsoft.Z3.dll
                  ImageRuntime=v4.0.30319
                  OriginalItemSpec=Microsoft.Z3
                  ReferenceSourceTarget=ResolveAssemblyReference
                  ResolvedFrom={HintPathFromItem}
                  Version=4.7.1.0
          C:\Users\ahelwer\source\test\Framework\lib\z3\libz3.dll
                  CopyLocal=true
                  FusionName=
                  HintPath=lib\z3\Microsoft.Z3.dll
                  OriginalItemSpec=C:\Users\ahelwer\source\test\Framework\lib\z3\Microsoft.Z3.dll
                  ResolvedFrom={HintPathFromItem}
                  Version=4.7.1.0 (TaskId:22)
  Task Parameter:
      DestinationFiles=
          bin\Debug\Microsoft.Z3.dll
                  CopyLocal=true
                  FusionName=Microsoft.Z3, Version=4.7.1.0, Culture=neutral, PublicKeyToken=9c8d792caae602a2
                  HintPath=lib\z3\Microsoft.Z3.dll
                  ImageRuntime=v4.0.30319
                  OriginalItemSpec=Microsoft.Z3
                  ReferenceSourceTarget=ResolveAssemblyReference
                  ResolvedFrom={HintPathFromItem}
                  Version=4.7.1.0
          bin\Debug\libz3.dll
                  CopyLocal=true
                  FusionName=
                  HintPath=lib\z3\Microsoft.Z3.dll
                  OriginalItemSpec=C:\Users\ahelwer\source\test\Framework\lib\z3\Microsoft.Z3.dll
                  ResolvedFrom={HintPathFromItem}
                  Version=4.7.1.0 (TaskId:22)

它变得更加神秘，因为如果我将libz3.dll移出目录，构建将失败，并显示以下错误:

It gets more mysterious, because if I take libz3.dll out of the directory, the build fails with the following error:

"C:\Users\ahelwer\source\test\Framework\FrameworkTest.csproj" (default target) (1) ->
(_CopyFilesMarkedCopyLocal target) ->
  C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\15.0\bin\Microsoft.Common.CurrentVersion.targe
ts(4358,5): error MSB3030: Could not copy the file "C:\Users\ahelwer\source\test\Framework\lib\z3\libz3.dll" because it
 was not found. [C:\Users\ahelwer\source\test\Framework\FrameworkTest.csproj]

即使我以标准方式在csproj中以<content/>引用libz3.dll！

Even if I reference libz3.dll in the standard way with <content/> in my csproj!

问题:

1. Microsoft.Z3.dll有什么特别之处，使它可以在构建过程中要求libz3.dll位于同一目录中?它带有某些标志吗?
2. 如何将这种效果添加到我自己的托管包装器库中?
3. 是否可以从Microsoft.Z3.dll中删除此效果，还是必须以其他方式重新编译它?