Open EXCEL (.xlsx) with password in C#

Question

I try to open password protected .xlsx files (Excel 2007 format) without typing the password manually. I have installed Excel 2003 and the Microsoft Office Compatibility Pack that converts the file when opening.

The following code works, but it prompt for the password.

Microsoft.Office.Interop.Excel.Application ExcelApp;
Microsoft.Office.Interop.Excel.Workbook ExcelWorkbook;
ExcelApp = new Microsoft.Office.Interop.Excel.Application();           
Object pwd = "xxx";
Object MissingValue = System.Reflection.Missing.Value;
ExcelWorkbook = ExcelApp.Workbooks.Open("C:\\temp\\test.xlsx",MissingValue, MissingValue, MissingValue,pwd);

If I use the same code to open a .xls File (Excel 2003), it works without prompting for the password. Opening .xlsx files without password protection also works fine.

How is it possible to open password protected .xlsx files without prompting for the password with Excel 2003 and the Microsoft Office Compatibility Pack?

The trick from a similar problem changing the readonly argument (3rd) to true

ExcelWorkbook = ExcelApp.Workbooks.Open("C:\\temp\\test.xlsx",MissingValue, true, MissingValue,pwd);

does not work here.

Answer 1

This may be late, but for any future person with Interop, for me it worked like this:

To open to write

var WFile = new Excel.Application();
Excel.Workbook Wbook = WFile.Workbooks.Open("myFilepath", ReadOnly: false, Password: "mypassword");

To open as read-only

var WFile = new Excel.Application();
Excel.Workbook Wbook = WFile.Workbooks.Open("myFilepath", ReadOnly: true, Password: "mypassword");