Correcting the order of building more than one project in visual studio solved the problem.

In my case, One project output binaries is references files for another project. When i changed the order, compilation was successful, but getting this error during the run time. Had all the necessary package, still getting the error. Later, it was found out and focused on the order of projects compilation in VS and avoided "Error: Cannot load file or assembly netstandard, Version=2.1.0.0" during the runtime.