webbrowser 禁用 alert

void web_Navigated(object sender, WebBrowserNavigatedEventArgs e)
        {
            var web = sender as System.Windows.Forms.WebBrowser;
            if (web.ActiveXInstance == null)
                return;

            HtmlElement head = web.Document.GetElementsByTagName("head")[];
            HtmlElement script = web.Document.CreateElement("script");
            IHTMLScriptElement element = (IHTMLScriptElement)script.DomElement;
            element.text = "function preventAlert() { window.alert = null; }";
            head.AppendChild(script);
            web.Document.InvokeScript("preventAlert");

            (web.ActiveXInstance as SHDocVw.WebBrowser).NewWindow2 += new SHDocVw.DWebBrowserEvents2_NewWindow2EventHandler(Form1_NewWindow2);
        }