I am popping up an HTML page from a Silverlight application using the HtmlPage.PopupWindow() method. I am trying to handle the event of when the popup window is closed from within Silverlight. This is how I am attempting to do this: var window = HtmlPage.PopupWindow(new Uri("http://mypopup..."), "popup", options); EventHandler<HtmlEventArgs> windowClosed = (sender, e) => { // would like to refresh the page when popup is closed... HtmlPage.Document.Submit(); }; window.AttachEvent("onUnload", windowClosed); However the event handler never seems to get called. Is this something that is possible or am I missing something? The Silverlight app and the HTML popup page are on the same domain, however they are actually on different ports. I was thinking that maybe the pages being on different ports would be considered a cross-site restriction and cause the JavaScript to fail.