How can i access foreign key data in database?

hello,
i am doing a project using asp.net plattform.I have to forms mainmenu and submenu.
i was taken menuid as a forain key in submenu table.
offcourse menuid is a primary key in the mainmenu table.
i want to show all menuid values from the table mainmenu table in to the submenu table.

how can i show that in the submenu table.is this any querry i have to write in to the form.
if yes then when i can fired that querry...plz tel me