使用ajax和模态窗口处理会话结束的最佳方法

I have a .NET MVC application which makes extensive use of AJAX and modal windows. I have an action filter that handles the expiration of a user's session which redirects to the login page. However, if the request is made from the modal window, the action result that is returned is the login page which then loads in the modal window. I have a .NET MVC application which makes exten