在WatiN浏览器中自定义BeforeNavigate事件

Question

我正在尝试通过修改"导航前"事件中的标题来使用WatiN框架更改用户代理字符串.我认为我真的很接近一个解决方案,但由于某种原因,我被重定向到一个空白页面,其中包含以下代码后,网址被访问了一秒左右.

如果我注释掉自定义BeforeNavigate事件,浏览器不会重定向到空白页面,这使我相信我的自定义事件需要稍作修改.你有任何想法可能是什么问题？

要重现此问题,请下载WatiN并运行以下代码:

private SHDocVw.InternetExplorerClass _ieInstance;

private const string UserAgent = 
   "User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64)" +
    "AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.153" + 
    "Safari/537.36\r\n";

bool _renavigating;
private IE _browser;

private void Form1_Load(object sender, EventArgs e)
{
    _ieInstance = _ieInstance = new SHDocVw.InternetExplorerClass();
    //_ieInstance.BeforeNavigate2 += BeforeNavigate;
    _browser = new IE(_ieInstance);
    _browser.GoTo("http://www.procato.com/my+headers/");
}

void BeforeNavigate(object pDisp, ref object url, ref object flags, 
     ref object targetFrameName, ref object postData, ref object headers, 
     ref bool cancel)
{
    if (!string.IsNullOrEmpty(UserAgent))
    {
        if (!_renavigating)
        {
            headers += string.Format("User-Agent: {0}\r\n", UserAgent);
            _renavigating = true;
            cancel = true;
            _ieInstance.Navigate((string)url, 
                 (string)targetFrameName, (byte[])postData, (string)headers);
        }
        else
        {
            _renavigating = false;
        }
    }
}

---

@ Noseratio的建议也给了我一个空白页面:

readonly SynchronizationContext _sc = SynchronizationContext.Current;

void BeforeNavigate(object pDisp, ref object url, ref object flags, 
     ref object targetFrameName, ref object postData, ref object headers, 
     ref bool cancel)
{
    if (!string.IsNullOrEmpty(UserAgent))
    {
        if (!_renavigating)
        {
            var newHeaders = string.Format("User-Agent: {0}\r\n", UserAgent);
            _renavigating = true;
            cancel = true;

            string thatUrl = (string)url;
            object thatFlags = flags;
            object thatTargetFrameName = targetFrameName;
            object thatPostData = postData;
            object thatHeaders = (headers != null && headers != Type.Missing && 
                               headers != System.DBNull.Value) ?
                (headers.ToString() + newHeaders) : newHeaders;

            _sc.Post(_ => 
            { 
                ((SHDocVw.IWebBrowser)pDisp).Navigate(
                    thatUrl, 
                    ref thatFlags,
                    ref thatTargetFrameName,
                    ref thatPostData,
                    ref thatHeaders);
            }, null);
        }
        else
        {
            _renavigating = false;
        }
    }
}

Answer 1

导航到页面的请求就足够了。

在这种情况下，我建议您放弃BeforeNavigate2, 并仅使用_ieInstance.Navigate来导航，从而使您的生活变得更简单。例如：

private void Form1_Load(object sender, EventArgs e)
{
    _ieInstance = _ieInstance = new SHDocVw.InternetExplorerClass();
    _browser = new IE(_ieInstance);
    _ieInstance.Navigate("http://www.procato.com/my+headers/", Headers: UserAgent);
}

procato 上显示的结果将是错误的标头，因为加载页面会发出额外的请求，而这些请求不会有正确的标头。但是，如果您使用 Fiddler2 这样的工具，您将看到初始请求具有正确的用户代理标头。