Unfortunately, if you have forgotten the password for your password-protected Excel file, there is no straightforward method to recover it. Microsoft does not provide a way to recover lost passwords for Excel files, and if you forget the password, you cannot unprotect the sheet or workbook. It is advisable to keep a list of your passwords in a safe place to avoid such situations in the future.
If you are looking to unprotect the workbook programmatically, you can use the Unprotect method in the Microsoft.Office.Interop.Excel namespace, but this requires you to know the password. Here’s a brief overview of the method:
public void Unprotect(object Password);
The Password parameter is required to unprotect the workbook, and if you omit it, the method will fail if the workbook is protected.
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