Replied 8 September 2017, 2:52 pm EST
You might be better off creating the class and passing the code to those who need to use it, as you will get licensing problems trying to use FpSpread from a DLL like you describe. Even if you manually add the licenses.licx with the FpSpread's type info to the DLL project and make it an embedded resource, the framework will not allow that embedded license to be used to create the control for clients of your DLL. Those clients would need to add the FpSpread's type into the licenses.licx for their EXE project, as if they are using FpSpread directly, so having the code in a DLL is less convenient that just having the source code.
If you really want to built the code into a DLL, you could do it in a UserControl, and if you don't create any FpSpread in design time (which should not be necessary for what you describe) then it should not require the Spread license if the UserControl is licensed. I made a blog post about this use case and how component licensing operates that you can refer to for more info:
<h4 class="BlogPostHeader">Licensing of .NET Components
You can create a FpSpread in code and use it without hosting it in a form to do what you describe. You don't need to have the control hosted on a form to load an Excel file or print to PDF.