Access to the database file is not allowed .sdf

Hi all ,

i am developing one application which is using SQL CE 3.5 for database.

 and i am putting at this path "C:\Users\demouser\AppData\Roaming\myApp"

but when i rum my setup i am getting the following error "Access to the database file is not allowed."

i searched about this and found that user account do have  read-only  permissions for application folder.

 how can i set the Read write permissions to user account code behind in c#?

please help me.

thanks