When you use the System.Web.HttpServerUtility.Transfer(string) method or use cross-page posting to transfer processing from one ASP.NET page to another, the originating page contains request information that might be required for the destination page. You can use the Page.PreviousPage property to access that information.

If the current page is being rendered as a result of a direct request (not a transfer or cross-post from another page), the Page.PreviousPage property contains null.