我正嘗試構建Web服務,並且應該使用現有的XML構建新的XML。在vb.net中構建XML文檔時,爲什麼會出現此錯誤
的代碼如下:
<WebMethod(CacheDuration:=0, Description:="GroveHallFromRss")> _
Public Function GroveHallFromRss() As XmlDocument
Dim webClient As System.Net.WebClient = New System.Net.WebClient()
Dim ourUrl As String = "http://123.example.org/RSSSyndicator.aspx?type=N&range=currentyear&expire=Y&location=2-7-165&rssid=18"
Dim stream AS Stream
stream = webClient.OpenRead(ourUrl)
Dim xmlDocument AS XmlDocument = new XmlDocument()
xmlDocument.Load(stream)
Dim myXml As XmlDocument = new XmlDocument()
Using writer As XmlWriter = myXml.CreateNavigator().AppendChild()
writer.WriteStartDocument()
writer.WriteStartElement("document")
For Each item As System.Xml.XmlElement In xmlDocument.Item("item")
writer.WriteStartElement("event")
writer.WriteElementString("title", item.Item("title").Value)
writer.WriteElementString("link", item.Item("link").Value)
writer.WriteElementString("description", item.Item("description").Value)
writer.WriteEndElement()
Next
writer.WriteEndElement()
writer.WriteEndDocument()
End Using
Return myXml
它給了我這樣的錯誤:
System.NullReferenceException:未設置爲一個對象的實例 對象引用。在Portal.GroveHallFromRss()
問題似乎是繞的線:
爲每個項目作爲System.Xml.XmlElement在xmlDocument.Item( 「項目」)
但我不確定是什麼造成了這一點。謝謝!
這裏去的XML:
<rss version="2.0">
-
<channel>
-
<title>
title 123
</title>
<cf:treatAs>list</cf:treatAs>
<link>http://123/default.aspx</link>
<description>RSS Feed 123 Events Calendar</description>
-
<item>
<title>New 123 (6/18/2012)</title>
-
<link>
http://123.aspx?view=EventDetails&eventidn=9751&information_id=19501&type=&rss=rss
</link>
-
<description>
<table cellpadding="5" cellspacing="0" border="0"><tr><td valign="top"><table cellpadding="0" cellspacing="0" border="0"><tr><td style="padding-bottom:1px;"><b>Start Date:</b> </td><td style="padding-bottom:1px;">6/18/2012</td><td> <b>Start Time:</b> </td><td>8:00 AM</td></tr><tr><td><b>End Date:</b> </td><td>6/18/2012</td><td> <b>End Time:</b> </td><td>4:00 PM</td></tr></table><br />123<br />Room: 123<br /><br />nil</td></tr></table>
</description>
<pubDate>Mon, 18 Jun 2012 12:00:00 GMT</pubDate>
<category>06/18/2012</category>
</item>
+
<item>
<title>123 Orientation (6/19/2012)</title>
-
<link>
http://123/EventList.aspx?view=EventDetails&eventidn=9770&information_id=19539&type=&rss=rss
</link>
-
<description>
<table cellpadding="5" cellspacing="0" border="0"><tr><td valign="top"><table cellpadding="0" cellspacing="0" border="0"><tr><td style="padding-bottom:1px;"><b>Start Date:</b> </td><td style="padding-bottom:1px;">6/19/2012</td><td> <b>Start Time:</b> </td><td>8:00 AM</td></tr><tr><td><b>End Date:</b> </td><td>6/19/2012</td><td> <b>End Time:</b> </td><td>4:00 PM</td></tr></table><br />123<br />Room: 106<br /><br />nil</td></tr></table>
</description>
<pubDate>Tue, 19 Jun 2012 12:00:00 GMT</pubDate>
<category>06/19/2012</category>
</item>
-
<item>
<title>123 (6/20/2012)</title>
-
<link>
http://123/EventList.aspx?view=EventDetails&eventidn=9789&information_id=19577&type=&rss=rss
</link>
-
<description>
<table cellpadding="5" cellspacing="0" border="0"><tr><td valign="top"><table cellpadding="0" cellspacing="0" border="0"><tr><td style="padding-bottom:1px;"><b>Start Date:</b> </td><td style="padding-bottom:1px;">6/20/2012</td><td> <b>Start Time:</b> </td><td>8:00 AM</td></tr><tr><td><b>End Date:</b> </td><td>6/20/2012</td><td> <b>End Time:</b> </td><td>4:00 PM</td></tr></table><br />123 Grove Hall<br />Room: 106<br /><br />nil</td></tr></table>
</description>
<pubDate>Wed, 20 Jun 2012 12:00:00 GMT</pubDate>
<category>06/20/2012</category>
</item>
</channel>
</rss>
發佈XML,它會幫助。 – Yatrix
是的我已經添加了XML,謝謝。 – eastboundr