Cannot access read-only document 'excel_filename.xls'

Question

Iam working on c# console. what iam trying to do is to get excel template and insert all records in in excell and create a copy to save the excel to network shared folder using a impersonated specific user..but the error was "Cannot access read-only document 'excel_filename.xls'."" please see my code snippet see error SaveAsCopy