I ran into a very weird issue with Nuget packages and the old packages.config reference style.
Nuget vs Semantic Versioning
Nuget grew up in Windows, where assembly version numbers support four numbers: major.minor.build.revision. Therefore, NugetVersion supports all four version segments. Semantic versioning, on the other hand, supports three numbers plus additional labels.
As part of Nuget’s version normalization, in an effort to better support semantic versioning, the fourth segment version is dropped if it’s zero. So 1.2.3.0 becomes 1.2.3. In general, this does not present any problems, since the version numbers are retrieved from the feed by the package manager tools and references updated accordingly.
Always use the tools provided
When you ignore the tooling, well, stuff can get weird. This is particularly true in the old packages.config reference style.
In that style, packages are listed in a packages.config file, and the .Net project file adds a reference to the DLL with a HintPath. That HintPath includes the folder where the package is installed, something like this:
<ItemGroup>
<Reference Include="MyCustomLibrary, Version=1.2.3.4, Culture=neutral, processorArchitecture=MSIL">
<HintPath>..\packages\MyCustomLibrary.1.2.3.4\lib\net472\MyCustomLibrary.dll</HintPath>
</Reference>
</ItemGroup>But, for argument’s sake, let us assume we publish a new version of MyCustomLibrary, version 1.2.4. Even though the AssemblyVersion might be 1.2.4.0, the Nuget version will be normalized to 1.2.4. And, instead of upgrading the package using one of the package manager tools, you just update the reference file manually, like this:
<ItemGroup>
<Reference Include="MyCustomLibrary, Version=1.2.4.0, Culture=neutral, processorArchitecture=MSIL">
<HintPath>..\packages\MyCustomLibrary.1.2.4.0\lib\net472\MyCustomLibrary.dll</HintPath>
</Reference>
</ItemGroup>This can cause weird issues. It will most likely build with a warning about not being able to find the DLL. Depending on how the package is used or referenced, you may not get a build error (I didn’t get one). But the build did not include the required library.
Moving on…
The “fix” is easy: use the Nuget tools (either the CLI or Visual Studio Package Manager) to update the packages. It will generate the appropriate HintPath for the package that is installed. An even better solution is to migrate to project reference style, where the project includes the Nuget references, and packages.config is not used. This presents immediate errors if an incorrect version is used.