Question

My connection string is:

String excelConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("abc.xls") + ";Extended Properties='Excel 8.0; HDR=YES;IMEX=1'";

OleDbConnection conn = new OleDbConnection(excelConn);  
Conn.Open();

It gives an error, like “Could not decrypt file.” If my Excel file (abc.xls) is close in my client PC. But it is ok when my excel file is open.

Answer 1

you cannot connect to a password protected excel file with OleDbConnection, it won’t work by design.

Check here: Open a password-protected Excel workbook

If you try to open a password-protected Excel workbook from Access,
you get an error message “Could not decrypt file”. Adding a Password=
value to your connection string won’t work either. You could open it
as an Excel application, but then you’d have to learn about the Excel
object model and all you want to do is read it row-by-row as you would
any unprotected Excel file.

To get around this problem, first open the Excel workbook using
GetObject() and then open it using the connection / recordset approach
that you want to use. The GetObject() open prompts your user for the
password, and then you are free to open the file using your preferred
approach.