Need a code for login and logout functionality using c #. i am using my sql as my database (Urgent)

hi, u r showing how to get the link button based on the Authentication.. i am new to this .net silverlight programming..so i need complete code for login and logout, i dont know how to store the values in database when we enter the login and log out values for the first time and need to validate when the user login with the same name and password.. is there any sample code for WPF windows phone applications...if so it will be easy for me to learn... thanks dude... for ur reply :)