ASP.NET Core - Exporting List To Excel

Hi guys, what is the recommended way to export a list to excel or csv?

I currently am developing a web app using Angular 2 and ASP.NET Core and I am generating a list in my back end that I send as JSON to the client side.  Since the list is already generated I would just like the file to be downloaded for the user.  In the past I would used OpenXML or some library but I do not believe those libraries exist to me in ASP.NET Core.

Here is a simplified idea of what I am doing I would just like to return that list to the user in the form of a CSV or Excel file.

 [HttpGet]
 [Route("/api/preview/{item}")]
 public IActionResult Preview(string item)
 {
     if (item!= null)
     {
         var preview = _context.dbPreview.FromSql("Exec sampleStoredProcedure {0}, 1", item).ToList();

         return Ok(preview);
     }
 }

Thanks