我正在尝试从下面提到的 url中提取link
usingxpath
string url = "http://www.album-cover-art.org/search.php?q=Ruin+-+Live+Album+Version+Lamb+of+God"
我的代码:
HtmlAgilityPack.HtmlWeb web = new HtmlAgilityPack.HtmlWeb();
HtmlAgilityPack.HtmlDocument htmlDoc = new HtmlAgilityPack.HtmlDocument();
htmlDoc = web.Load(url); //Exception generated here Line 23
if (htmlDoc.DocumentNode != null)
{
HtmlNode linkNode = htmlDoc.DocumentNode.SelectSingleNode(".//*[@id='related_search_row']/img/@src");
if (linkNode != null)
Console.WriteLine(linkNode.InnerText);
}
上面的代码编译得很好,但是当我尝试运行它时会产生异常
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object.
完整的堆栈跟踪
System.NullReferenceException: Object reference not set to an instance of an object.
at HtmlAgilityPack.HtmlDocument.ReadDocumentEncoding(HtmlNode node) in C:\Source\htmlagilitypack\Trunk\HtmlAgilityPack\HtmlDocument.cs:line 1916
at HtmlAgilityPack.HtmlDocument.PushNodeEnd(Int32 index, Boolean close) in C:\Source\htmlagilitypack\Trunk\HtmlAgilityPack\HtmlDocument.cs:line 1805
at HtmlAgilityPack.HtmlDocument.Parse() in C:\Source\htmlagilitypack\Trunk\HtmlAgilityPack\HtmlDocument.cs:line 1468
at HtmlAgilityPack.HtmlDocument.Load(TextReader reader) in C:\Source\htmlagilitypack\Trunk\HtmlAgilityPack\HtmlDocument.cs:line 769
at HtmlAgilityPack.HtmlWeb.Get(Uri uri, String method, String path, HtmlDocument doc, IWebProxy proxy, ICredentials creds) in C:\Source\htmlagilitypack\Trunk\HtmlAgilityPack\HtmlWeb.cs:line 1515
at HtmlAgilityPack.HtmlWeb.LoadUrl(Uri uri, String method, WebProxy proxy, NetworkCredential creds) in C:\Source\htmlagilitypack\Trunk\HtmlAgilityPack\HtmlWeb.cs:line 1563
at HtmlAgilityPack.HtmlWeb.Load(String url, String method) in C:\Source\htmlagilitypack\Trunk\HtmlAgilityPack\HtmlWeb.cs:line 1149
at HtmlAgilityPack.HtmlWeb.Load(String url) in C:\Source\htmlagilitypack\Trunk\HtmlAgilityPack\HtmlWeb.cs:line 1107
at ScreenScrapping.Program.Main(String[] args) in c:\Users\ranveer\csharp\ScreenScrapping\ScreenScrapping\Program.cs:line 23
所以,我的问题是为什么我会得到这个例外。