programatically password protect the excel sheet from the disk

I have an existing Excel file. I need to programatically password protect the file so that it can't be read unless the user provide the password.

I donot want to use INTEROP object like this

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Please i donot want to use Excel.Application object or interop object.

Suppose my excel sheet is present at C:\temp\cost.xls.

I am generated the excel sheet using XSLT/XML .

Please provide any other way to protect my excel sheet.

Many Thanks.

Hello anshuman.mohanty,

To set a password through code, you have to interact with the Excel Application Object as all passwords are properties of the objects belonging to Excel. This is true regardless of the language used: C++, Java, VBA, Interop, etc.