HtmlAgilityPack 错误：对象引用未设置为对象的实例

Question

我已经使用这个代码好几个月了，它对我来说工作得很好，但现在我收到了这个错误：Object reference not set to an instance of an object. 在这行代码：

Dim Page_Most_Recent_Quarter As Date = document.DocumentNode.SelectSingleNode("//*[@id='financials-iframe-wrap']/div/table//tr[2]/th[3]").InnerText

这里是完整的代码：

Dim wreq As HttpWebRequest = WebRequest.Create("http://www.nasdaq.com/symbol/GOOG/financials?query=income-statement&data=quarterly")
    wreq.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.5) Gecko/20091102 Firefox/3.5.5"
    wreq.Method = "get"
    Dim prox As IWebProxy = wreq.Proxy
    prox.Credentials = CredentialCache.DefaultCredentials
    Dim document As New HtmlAgilityPack.HtmlDocument
    Dim web As New HtmlAgilityPack.HtmlWeb
    web.UseCookies = True
    web.PreRequest = New HtmlAgilityPack.HtmlWeb.PreRequestHandler(AddressOf onPreReq)
    wreq.CookieContainer = cookies
    Dim res As HttpWebResponse = wreq.GetResponse()
    document.Load(res.GetResponseStream, True)
    Dim Page_Most_Recent_Quarter As Date = document.DocumentNode.SelectSingleNode("//*[@id='financials-iframe-wrap']/div/table//tr[2]/th[3]").InnerText

我认为没有任何更改会影响此代码。我无法弄清楚出了什么问题。

Answer 1

我猜该节点不存在或已被重命名。这是一个公共网站，会随时更改他们的内容。因为它没有找到它，所以它是 NOTHING，你不能在 nothing 上执行 .InnerText。

尝试将document.DocumentNode.SelectSingleNode("//*[@id='financials-iframe-wrap']/div/table//tr[2]/th[3]") 放入另一个变量并在调试时检查它。