It's telling you to check for an empty string by checking its Length, not comparing it to the reference of String.Empty.
if (dataFileLine[10].Trim().Length == 0
|| dataFileList[15].Trim().Length == 0
....
The tiny little problem with that is if any of those dataFileLine[] references returns null the call to Trim will fail with a "Object not set to an instance of an object" error.