Live SpreadsheetGear API Samples
Workbook Opening Password-Protected Files
SpreadsheetGear supports reading and writing encrypted workbooks with Agile Encryption used by Excel 2013 and later, including default SHA-512 encryption for workbooks.
// First create an empty workbook set. SpreadsheetGear.IWorkbookSet workbookSet = SpreadsheetGear.Factory.GetWorkbookSet(); // Now open password-protected file within this workbook set, specifying the password as the second argument. SpreadsheetGear.IWorkbook workbook = workbookSet.Workbooks.Open(@"c:\path\to\workbook.xlsx", "MyPassword1234");