R – Load File in XAP

I had a number of CSV files embedded within a Silverlight DLL (as Resource). I need to move these into the XAP (as Content rather than resource). The trouble is Application.GetResourceStream always seems to return null when I try and access the files. I have tried a number of ways to achieve this but can't seem to do it. How do you reference the CSV files from code behind?

Thanks in advance.