c# 윈폼 웹브라우저 경고창 차단하기

private void wb_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
    webBrowser1.ScriptErrorsSuppressed = true;
    if (e.Url.AbsoluteUri == webBrowser1.Url.AbsoluteUri)
    {
    }
}

위처럼 해서 안되면
private void webBrowser1_Navigated(object sender, WebBrowserNavigatedEventArgs e)
        {
            HtmlElement he = webBrowser1.Document.GetElementsByTagName("head")[0];
            HtmlElement se = webBrowser1.Document.CreateElement("script");
            mshtml.IHTMLScriptElement element = (mshtml.IHTMLScriptElement)se.DomElement;
            string alertBlock = "window.alert = function () { }";
            element.text = alertBlock;
            he.AppendChild(se);
        }