Sys.Application.add_load(WireEvents);
Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(PageLoadedHandler)
Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler);
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);

function WireEvents() { }

function BeginRequestHandler(sender, args) {}

function EndRequestHandler(sender, args) {
    
    if (args.get_error() != undefined && args.get_error().httpStatusCode == '500') {
        var errorMessage = args.get_error().message
        args.set_errorHandled(true);
        alert(errorMessage);
    } 
    
    try {
        AfterRequestHandler();
    } catch (e) { }

}

function PageLoadedHandler(sender, args) {
    try {
        AfterRequestHandler();
    } catch (e) { }
}