asp.net membership comparing current logged on user password change and creation dates -

protected void login2_loggedin(object sender, eventargs e) {         if (membership.getuser().lastpasswordchangeddate == membership.getuser().creationdate)     {         response.redirect("changepassword.aspx");     } } 

as can see im wanting force password changes on first login. not doing correctly. examples tried use appear have built own login controls. using built in login control i'm not sure how handle text boxes uses.

the error getting on if statement "object reference not set instance of object. "

thank help.