A quick explanation of how to do a user logoff in asp.net while using forms authentication.

It is actually very simple. All you need is to create a logout.aspx page and add the following code. Then to logoff any users from anywhere in your application simply link to the page /Logout.aspx. Redirecting to the logout page will also work.

public partial class Logout : AppPage
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (User.Identity.IsAuthenticated)
        {
            Session.Clear();
            FormsAuthentication.SignOut();
            Response.Redirect("Logout.aspx");
        }
    }
}