Help in login form

hello .

i am new to asp.net.

when i add a login form to my page, the database file (aspnetdb.mdf) does not appears in app-data folder, i have refreshed it but nothing happened,

first time when i was trying one of the login forms, i deleted the aspnetdb.mdf file , but in my new projects it is not
appering.

so plz help how to get it.

thx

mansoor