I have a shared project (lets call it SharedProject) that I am using in more than one solution. This SharedProject is not in the same folder as either solution but sits in a sibling folder to these solutions.
When I create a Jenkins job and link it to my sln file, it does not pull the SharedProjectinto the Jenkins job workspace. When running the Jenkins job it tells me that the SharedProject.csproj file cannot be found in the current context.

For Example:
the Shared Project sits at C:/Code/Share/SharedProject.csproj
the solution sits as C:/Code/Project/Solution.sln

In my Visual Studio solution file it refers to the SharedProject as ../Share/SharedProject.csproj, this path is not in the Jenkins workspace.