Redirection to another page from a custom widget

I have a custom widget that has an ajax post. This accesses a method in a controller which has the following code:

 [HttpPost]
        public void CompareTariffs(string selection)
       
            Response.Redirect("~/Default.aspx");
       

However the page just refreshes and remains on the same page, it does not redirect to the other page. Would anyone know why this is happening?