我得到WebException上的url为什么是这样的？

Question

我有这样的代码：

private List<string> webCrawler(string url, int levels) 
     { 
      HtmlAgilityPack.HtmlDocument doc; 
      HtmlWeb hw = new HtmlWeb(); 
      List<string> webSites; 
      List<string> csFiles = new List<string>(); 

      csFiles.Add("temp string to know that something is happening in level = " + levels.ToString()); 
      csFiles.Add("current site name in this level is : "+url); 

      doc = hw.Load(url); 
      webSites = getLinks(doc); 


      if (levels == 0) 
      { 
       return csFiles; 
      } 
      else 
      { 
       int actual_sites = 0; 
       for (int i = 0; i < webSites.Count() && i< 20; i++)     { 
        string t = webSites[i]; 
             if ((t.StartsWith("http://")==true) || (t.StartsWith("https://")==true))      { 
         actual_sites++; 
         csFiles.AddRange(webCrawler(t, levels - 1)); 
         Texts(richTextBox1, "Level Number " + levels + " " + t + Environment.NewLine, Color.Red); 
        } 
       } 

       return csFiles; 
      } 


     } 

而且getLinks（）是：

private List<string> getLinks(HtmlAgilityPack.HtmlDocument document) 
     { 

      List<string> mainLinks = new List<string>(); 
      var linkNodes = document.DocumentNode.SelectNodes("//a[@href]"); 
      if (linkNodes != null) 
      { 
       foreach (HtmlNode link in linkNodes) 
       { 
        var href = link.Attributes["href"].Value; 
        mainLinks.Add(href); 
       } 
      } 
      return mainLinks; 

     } 

问题是，比如我爬进google.com如此几次后，其获得的网站：

http://picasa.google.co.il/intl/iw/#utm_source=iw-all-more&utm_campaign=iw-pic&utm_medium=et

然后即时得到就行了异常：

doc = hw.Load(url); 

的错误是：远程名称不能被解析：picasa.google.co.il'

唯一的例外是：

System.Net.WebException was unhandled 
    Message=The remote name could not be resolved: 'picasa.google.co.il' 
    Source=System 
    StackTrace: 
     at System.Net.HttpWebRequest.GetResponse() 
     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 1446 
     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 1152 
     at HtmlAgilityPack.HtmlWeb.Load(String url) in C:\Source\htmlagilitypack\Trunk\HtmlAgilityPack\HtmlWeb.cs:line 1107 
     at GatherLinks.Form1.webCrawler(String url, Int32 levels) in D:\C-Sharp\GatherLinks\GatherLinks\GatherLinks\Form1.cs:line 79 
     at GatherLinks.Form1.webCrawler(String url, Int32 levels) in D:\C-Sharp\GatherLinks\GatherLinks\GatherLinks\Form1.cs:line 108 
     at GatherLinks.Form1.webCrawler(String url, Int32 levels) in D:\C-Sharp\GatherLinks\GatherLinks\GatherLinks\Form1.cs:line 108 
     at GatherLinks.Form1..ctor() in D:\C-Sharp\GatherLinks\GatherLinks\GatherLinks\Form1.cs:line 31 
     at GatherLinks.Program.Main() in D:\C-Sharp\GatherLinks\GatherLinks\GatherLinks\Program.cs:line 18 
     at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) 
     at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) 
     at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() 
     at System.Threading.ThreadHelper.ThreadStart_Context(Object state) 
     at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) 
     at System.Threading.ThreadHelper.ThreadStart() 
    InnerException: 

我怎样才能修复/修复/解决？

谢谢。

Answer 1

例外情况是告诉您它无法将picasa.google.co.il解析为IP地址。您可能只需要验证名称是否正确。

打开命令窗口，键入：

ping picasa.google.co.il 

你会发现，你的电脑不能与此服务器，因为没有它DNS条目。