EDIT EXCEL C#

The following program open an Excel and save to CSV.

Reference to Microsfot.Office.Interop.Excel

Microsoft.Office.Interop.Excel.Application app = new Microsoft.Office.Interop.Excel.Application();

Microsoft.Office.Interop.Excel.Workbooks workbooks;

Microsoft.Office.Interop.Excel.Workbook workbook;

Microsoft.Office.Interop.Excel.Sheets sheets;

 Microsoft.Office.Interop.Excel.Worksheet worksheet;

//don't use 'two dots' such as workbook = app.workbooks.open(path), this will create all the com objects on the path and make it hard to be released

workbooks = app.Workbooks;

workbook = workbooks.Open(path);

sheets = workbook.Worksheets;

worksheet = sheets[1];

worksheet.SaveAs(file_full_path, Microsoft.Office.Interop.Excel.XlFileFormat.xlCSVWindows,

                                     false, false, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlNoChange,

                                     Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);

workbook.Close(true, Type.Missing, Type.Missing);//save changes = true, so it won't prompt to save or discard

//release the com objects are important, otherwise it will keep the process EXCEL.exe running in the background

 GC.Collect();

 GC.WaitForPendingFinalizers();

 System.Runtime.InteropServices.Marshal.ReleaseComObject(sheets);

 System.Runtime.InteropServices.Marshal.ReleaseComObject(worksheet);

 System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook);

System.Runtime.InteropServices.Marshal.ReleaseComObject(workbooks);