请看下面的代码,因为我在这一行得到错误:
xslt.Transform(mydoc.CreateReader(), writer);
错误:
步入:跨过非用户代码“System.Xml.Linq.XNode.CreateReader” System.Data.SqlXml.dll 中发生“System.NullReferenceException”类型的第一次机会异常
((System.NullReferenceException)(ex))
PromotionsDataContext db = new PromotionsDataContext();
//XmlDocument myxml;
XElement Categories =
new XElement("Promotions",
from b in db.GetPromotions()
select new XElement("Promotion",
new XElement("Category", b.CategoryName),
new XElement("Client", b.ClientName),
new XElement("Title", b.Title)));
XDocument mydoc = new XDocument();
mydoc.Add(Categories);
try
{
XDocument newTree = new XDocument();
XmlWriterSettings settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
settings.ConformanceLevel = ConformanceLevel.Fragment;
settings.CloseOutput = false;
//using (XmlWriter writer = newTree.CreateWriter())
using (XmlWriter writer = XmlWriter.Create(newTree.CreateWriter(), settings))
{
// Load the style sheet.
XslCompiledTransform xslt = new XslCompiledTransform();
xslt.Load(XmlReader.Create(new FileStream(@"C:\1\TransList.xslt", System.IO.FileMode.Open)));
// Execute the transform and output the results to a writer.
xslt.Transform(mydoc.CreateReader(), writer);
}
Console.WriteLine(newTree);
}
catch (Exception ex)
{
Console.Write(ex);
}
这是 XSLT:
<xsl:stylesheet version='1.0' xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>
<xsl:output method='xml' />
<xsl:key name='categories' match='Category' use='.' />
<xsl:template match='/'>
<xsl:for-each select="/Promotions/Promotion/Category[
generate-id(.) = generate-id(key('categories', .)[1])
]">
<xsl:variable name='cname' select='.' />
<Category title='{.}'>
<xsl:for-each select='/Promotions/Promotion[Category=$cname]'>
<Title>
<xsl:value-of select='Title' />
</Title>
</xsl:for-each>
</Category>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
错误:
System.NullReferenceException:对象引用未设置为对象的实例。在 System.Xml.Xsl.Runtime.XmlMergeSequenceWriter.StartTree(XPathNodeType rootType, IXmlNamespaceResolver nsResolver, XmlNameTable nameTable) 在 System.Xml.Xsl.Runtime.XmlQueryOutput.StartTree(XPathNodeType rootType) 在 System.Xml.Xsl.Runtime.XmlQueryOutput.WriteStartRoot () 在 Root(XmlQueryRuntime {urn:schemas-microsoft-com:xslt-debug}runtime) 在 Execute(XmlQueryRuntime {urn:schemas-microsoft-com:xslt-debug}runtime) 在 System.Xml.Xsl.XmlILCommand.Execute System.Xml.Xsl.XmlILCommand.Execute(XmlReader contextDocument, XmlResolver dataSources, XsltArgumentList argumentList, XmlWriter results) 在 System.Xml.Xsl 的(对象 defaultDocument、XmlResolver dataSources、XsltArgumentList argumentList、XmlWriter writer、Boolean closeWriter)。
现在,如果我这样做,它会起作用:
StringWriter sw = new StringWriter();
xslt.Transform(mydoc.CreateReader(),null, sw);
我对 XmlWriter 做错了什么?
崩溃前 xdoc 的值:
<Promotions>
<Promotion>
<Category>Arts & Entertainment</Category>
<Client>Client1</Client>
<Title>Get your Free 2</Title>
</Promotion>
<Promotion>
<Category>Arts & Entertainment</Category>
<Client>Client1</Client>
<Title>Get your Free 4</Title>
</Promotion>
<Promotion>
<Category>Arts & Entertainment</Category>
<Client>client1</Client>
<Title>Get your Free 5</Title>
</Promotion>
<Promotion>
<Category>Community & Neighborhood</Category>
<Client>Client2</Client>
<Title>Get your Free 1</Title>
</Promotion>
<Promotion>
<Category>Education</Category>
<Client>Client3</Client>
<Title>Get Your Free 3</Title>
</Promotion>
</Promotions>