Package restore of sln fails, but each individual project succeeds

[AArnott]

d15rel 26228.0

git clone https://github.com/aarnott/pinvoke
cd pinvoke
git checkout bugrepro/roslyn-project-system/1678
cd src
msbuild /t:restore

Package restore mostly succeeds, but fails with these two errors:

   "C:\git\pinvoke\src\PInvoke.sln" (restore target) (1) ->
  (Restore target) ->
    C:\Program Files (x86)\Microsoft Visual Studio\2017\d15rel\Common7\IDE\CommonExtensions\Microsoft\NuGet\NuGet.targets(97,5): error : Unable to resolve 'C:\git\pinvoke\src\NtDll\NtDll.csproj' for '.NETFramework,Version=v4.6'. [C:\git\pinvoke\src\PInvoke.sln]
    C:\Program Files (x86)\Microsoft Visual Studio\2017\d15rel\Common7\IDE\CommonExtensions\Microsoft\NuGet\NuGet.targets(97,5): error : Unable to resolve 'C:\git\pinvoke\src\Wtsapi32\Wtsapi32.csproj' for '.NETFramework,Version=v4.0'. [C:\git\pinvoke\src\PInvoke.sln]

Yet when I do a package restore on each individual project in the solution, I get no errors:

gci *csproj -rec |% { write-host -foreground green $_; msbuild /nologo /m /v:minimal /t:restore $_ }

[jonasric]

I'm experiencing the same issue, where using MSBuild /t:Restore to restore many projects together is failing with error similar to: "error : Unable to resolve '<my common .csproj>' for '.NETFramework,Version=v4.5'.

In my case, this error appears for several projects, and they're all referring to the same <my common .csproj>, which is a common project that almost all other projects reference (by ProjectReference).

Some projects that were failing to restore with this error succeeded when I restored them individually, as mentioned in the OP. However, other projects still fail with the same error even when I restore them (with msbuild /t:restore) individually.

Is there a known workaround that I can try until a fix is ready?

[emgarten]

I'm not able to repro this in NuGet 4.4/VS 15.4 using the steps above. This is has likely been fixed.

Let me know if you are seeing this issue still.

[AArnott]

Agreed. This is gone in the latest builds. Thanks.

[jonasric]

To close the loop on this one- yes it is gone. After some more investigation and experimentation, I found the issue I was experiencing was related to #2901. Namely, when some common project is referenced by multiple other projects in the dependency graph, using ProjectReference items but with different string-casing (e.g one project references 'SomeCommonProject.csproj', and another references 'somecommonproject.csproj'), the issue happens. After normalizing the casing of all ProjectReference references, the issue was resolved for me.

[emgarten]

@jonasric you were likely hitting #5855