How to diagnose warning MSB3277: Found conflicts between different versions of the same dependent assembly that could not be resolved

Question

I'm getting an annoying MSB3277 warning when I build my project. I increased verbosity to "detailed" and I was able to get the following information from the log:

      There was a conflict between "Pathoschild.Http.Client, Version=3.0.0.0, Culture=neutral, PublicKeyToken=null" and "Pathoschild.Http.Client, Version=3.1.0.0, Culture=neutral, PublicKeyToken=null".
         "Pathoschild.Http.Client, Version=3.0.0.0, Culture=neutral, PublicKeyToken=null" was chosen because it was primary and "Pathoschild.Http.Client, Version=3.1.0.0, Culture=neutral, PublicKeyToken=null" was not.

         References which depend on "Pathoschild.Http.Client, Version=3.0.0.0, Culture=neutral, PublicKeyToken=null" [C:\Users\desau\.nuget\packages\pathoschild.http.fluentclient\3.0.0\lib\netstandard1.3\Pathoschild.Http.Client.dll].
             C:\Users\desau\.nuget\packages\pathoschild.http.fluentclient\3.0.0\lib\netstandard1.3\Pathoschild.Http.Client.dll
               Project file item includes which caused reference "C:\Users\desau\.nuget\packages\pathoschild.http.fluentclient\3.0.0\lib\netstandard1.3\Pathoschild.Http.Client.dll".
                 C:\Users\desau\.nuget\packages\pathoschild.http.fluentclient\3.0.0\lib\netstandard1.3\Pathoschild.Http.Client.dll

         References which depend on "Pathoschild.Http.Client, Version=3.1.0.0, Culture=neutral, PublicKeyToken=null" [].
             C:\Users\desau\.nuget\packages\stronggrid\0.30.0\lib\netstandard1.3\StrongGrid.dll
               Project file item includes which caused reference "C:\Users\desau\.nuget\packages\stronggrid\0.30.0\lib\netstandard1.3\StrongGrid.dll".
                 C:\Users\desau\.nuget\packages\stronggrid\0.30.0\lib\netstandard1.3\StrongGrid.dll

If I understand this log correctly, it's telling me that my project references Pathoschild.Http.Client version 3.0 and also version 3.1. I understand the reference to version 3.1 because my project references a nuget package called StrongGrid which itself references Pathoschild version 3.1

But I fail to understand where the reference to version 3.0 comes from.

I'm using Visual Studio 2017 and MSBuild 15 in case that's helpful information.

Answer 1

The reason for this issue is that the StrongGrid package is authored incorrectly.

The version 0.30 of StrongGrid is built against version 3.1.0 of Pathoschild.Http.FluentClient, but their .nuspec file used for creating the NuGet package still lists version 3.0.0 as dependency, so the consuming project will fetch an older version, creating a conflict that cannot be resolved.

To work around this problem, you can explicitly reference version 3.1.0 of Pathoschild.Http.FluentClient by adding a package reference to the csproj file to override the version.