Unable to access the dll created in VS2008 which returns a dataset in .NET core webAPI

Hi,

I have a project in VS 2008 which has a method and returns a dataset. 

Now I created a webAPI in VS 2017 .net core project. 

I have referred the vs 2008 project in the .net core 2017 web API project. I am able to create object reference and access the method.

It builds the project without any error and when I run the web API it says it couldn't access the dll.

The error I get is System.IO.FileNotFoundException:'Could not load file or asssembly'

Thanks !!!