C# Reflection - Use reflection to call a method [duplicate]

This method that downloads files is being flagged as a possible path traversel security flaw, I've tried a few things, but nothing solves, my last alternative is to use reflection to hide the type and the checkmarx scan no longer identifies how being a method that handles file download

I understand that I would have to use reflection in the ReadAllBytes method and maybe change the return

I'm having trouble implementing the Index code via reflection

public ActionResult Index(string fileName)
     {
          string rootPath = System.Configuration.ConfigurationManager.AppSettings.Get("FinalUploadFolder");
          byte[] fileBytes = System.IO.File.ReadAllBytes(string.Format(Path.Combine(rootPath, fileName.ToString())));
          return File(fileBytes, System.Net.Mime.MediaTypeNames.Application.Octet, fileName.ToString());
     }