Check the build log for any errors and warnings from MSBuild.
Make sure that you provide a link to the project, but not to the exit of the project.
Verify that the compilation of ClassLibrary1 succeeded.
Yes, the .sln file must contain the required information.
Could you try running the assembly from the console using msbuild.exe. It works? msbuild.exe mySolution.sln / t: Repair
Try targeting Rebuild
What user account is used to start the build agent windows service?
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