1) OleDB: http://www.c-sharpcorner.com/UploadFile/yuanwang200409/how-to-convert-xls-file-into-csv-file-in-C-Sharp/
2) interop.service: https://stackoverflow.com/questions/2536181/is-there-any-simple-way-to-convert-xls-file-to-csv-file-excel
3) OleDB and DataAdapter: http://dklee.net/46
