1，首先引入using mshtml;在类名称前添加[ComVisible(true)]

2，在webBrowser1.Navigate("http://xxxxx")时,添加事件 webBrowser1.Navigated+=new WebBrowserNavigatedEventHandler(webBrowser1_Navigated);（webBrowser1为webBrowser控件实例）

3，在webBrowser1_Navigated函数中添加如下内容：

public void webBrowser1_Navigated(object sender, WebBrowserNavigatedEventArgs e)

{

                IHTMLWindow2 win = (IHTMLWindow2)webBrowser1.Document.Window.DomWindow;
                string s = @"function confirm() {";
                s += @"return true;";
                s += @"}";
                s += @"function alert(str)";
                s += @"{";
                s += @"window.external.alertMessage(str);";
                s += @"}";
                win.execScript(s, "javascript");
                webBrowser1.ObjectForScripting = this;

}

alertMessage(str)为自定义函数，形式如下：

      public void alertMessage(string s)
        {

           MessageBox.Show("接收到alert消息："+s); //换成你自己想要执行的动作

        }