XPath扩展方法在.NET 3.5中失败，在.NET 4.0中有效

Question

我创建了一个标准的XsltContext类，并按如下方式调用它：

        XPathCustomContext context = new XPathCustomContext(new NameTable());
        context.AddNamespace("windward", XPathCustomContext.Namespace);
        XsltArgumentList varList = new XsltArgumentList();
        varList.AddParam("stat-index", "", 0);
        context.ArgList = varList;
        XmlDocument doc = new XmlDocument();
        doc.Load("c:\test\order.xml");
        object xx = doc.CreateNavigator().Evaluate("/order[1]/customer[1]/num[@negone = $stat-index]", context);

当在.net 4.0下运行时，它运行良好。但在.NET 3.5(我们目前必须使用(下，我得到了：

System.Xml.XPath.XPathException was unhandled
  Message=XsltContext is needed for this query because of an unknown function.
  Source=System.Xml
  StackTrace:
       at MS.Internal.Xml.XPath.CompiledXpathExpr.UndefinedXsltContext.ResolveVariable(String prefix, String name)
       at MS.Internal.Xml.XPath.VariableQuery.SetXsltContext(XsltContext context)
       at MS.Internal.Xml.XPath.LogicalExpr.SetXsltContext(XsltContext context)
       at MS.Internal.Xml.XPath.FilterQuery.SetXsltContext(XsltContext input)
       at MS.Internal.Xml.XPath.CompiledXpathExpr.SetContext(XmlNamespaceManager nsManager)
       at System.Xml.XPath.XPathExpression.Compile(String xpath, IXmlNamespaceResolver nsResolver)
       at System.Xml.XPath.XPathNavigator.Evaluate(String xpath, IXmlNamespaceResolver resolver)
       at CustomXpathFunctions.Program.Main(String[] args) in c:srcCustomXpathFunctionsProgram.cs:line 62
       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: 

知道为什么吗？

示例代码位于http://www.windwardreports.com/temp/CustomXPathFunctionsBug.zip

感谢-dave

Answer 1

找到了一种方法。使用XPathExpression，如：

XPathNavigator nav = doc.CreateNavigator();
XPathExpression exp = nav.Compile("/order[1]/customer[1]/num[@negone = $stat]");
exp.SetContext(ctx);
object zzz = nav.Evaluate(exp);

至于原因，我的猜测是Evaluate(字符串，上下文(只在.NET3.5中将其用于命名空间，而XPathExpression则将其用于所有内容。但关键的一点是，这是有效的。

ps-请投票支持这个答案——这真的很难弄清楚。