"Sébastien Ros" <SbastienRos@discussions.microsoft.com> wrote in message
news:4BCD58AC-EB4F-468B-9AF8-16B6001F8BFF@microsoft.com...
> During the process of an XML document, I have to make a SelectNodes() call
on
> an XmlDocument. It returns an isntance of XPathNodeList. I can call it
> several times but at one point, the result can't be iterated.
>
> Here is the code:
>
> XmlNodeList nodes = _Document.SelectNodes(myXpathQuery);
> foreach(XmlNode n in nodes)
> { ... }
>
> While debugging, a NullReferenceException is thrown, but the cursor points
> to the keyword "in" in the the foreach statement. It means that it occured
in
> the internal Enumerator. Moreover, if I put a breakpoint before the
foreach
> statement and try to watch into "nodes", the Count property evaluation
throws
> this NullReferenceException. The second time I evaluate the "Count"
> everything it returns 0 (although it should be 2).
>
> Unfortunately, if I take the same document with the same xpath query in a
> virgin console application, I can't reproduce it, ecerything is ok.
>
> Any advice is welcome.
>
> --
> Sébastien Ros
> Evaluant - CTO

>

>

>

"Sébastien Ros" <SbastienRos@discussions.microsoft.com> wrote in message
news:6B41E0F3-708B-410F-9B05-FFE0942ED51C@microsoft.com...
> It occurs when I make an xpath query using the id() operator, but it
doesn't
> occur everytime. It can take several other queries on this document before
it
> occurs.
>
> Here are the details:
>
> Exception:
> System.NullReferenceException {"Object reference not set to an instance of
> an object."}
>
> Source :
> System.Xml
>
> StackTrace :
> at System.Xml.XmlDocument.GetElementById(String elementId)
> at System.Xml.DocumentXPathNavigator.MoveToId(String id)
> at MS.Internal.Xml.XPath.IDQuery.ProcessIds(String val)
> at MS.Internal.Xml.XPath.IDQuery.advance()
> at MS.Internal.Xml.XPath.XPathSelectionIterator.MoveNext()
> at MS.Internal.Xml.XPath.XPathNodeList.ReadUntil(Int32 index)
> at MS.Internal.Xml.XPath.XmlNodeListEnumerator.MoveNext()
>
> The code executed when it occured: (the debugger points the "in", so it
> happens in SelectNodes() )
>
> string xPath = "id('230b2b34-8eb4-408e-a817-4c055525bafa')";
> foreach(XmlNode n in _Document.SelectNodes(xPath))
> {
> ...
> }
>
> The xml document:
>
> <!DOCTYPE USS[
> <!ELEMENT USS (Entity*)>
> <!ELEMENT Entity (Reference*, Attribute*)>
> <!ELEMENT Reference EMPTY>
> <!ELEMENT Attribute (#PCDATA)>
> <!ATTLIST Entity
> Type CDATA #REQUIRED
> Id ID #REQUIRED
> >
> <!ATTLIST Reference
> Role CDATA #REQUIRED
> RefId IDREF #REQUIRED
> >
> <!ATTLIST Attribute
> Type CDATA #REQUIRED
> Name CDATA #REQUIRED
> >
> ]>
> <USS>
> <Entity Type="EPT:Priority" Id="b55b67a9-a941-4a25-bea0-22c5dd2ccebf">
> <Attribute Name="Name" Type="System.String">3 - Urgent</Attribute>
> </Entity>
> <Entity Type="EPT:State" Id="b96d364d-aa9d-4dc3-a468-78d66ac050d9">
> <Attribute Name="Description" Type="System.String">The case is new and
> active</Attribute>
> <Attribute Name="Name" Type="System.String">Opened</Attribute>
> <Attribute Name="ClosesCase" Type="System.Boolean">False</Attribute>
> </Entity>
> <Entity Type="EPT:Priority" Id="51b3d245-cd32-4396-8553-18f77398d666">
> <Attribute Name="Name" Type="System.String">If Time</Attribute>
> </Entity>
> <Entity Type="EPT:Category" Id="1a672d3a-a8d2-49b6-9de6-52ff69b275fb">
> <Attribute Name="Name" Type="System.String">Request</Attribute>
> <Attribute Name="Bitmap"
> Type="System.String">~/images/app/email.gif</Attribute>
> </Entity>
> <Entity Type="EPT:Priority" Id="fb04e846-d592-4650-bb24-4ea905c8d8ce">
> <Attribute Name="Name" Type="System.String">1 - Urgent</Attribute>
> </Entity>
> <Entity Type="EPT:State" Id="b8ad8d84-c580-49fc-9ea1-6c3a8e85141e">
> <Attribute Name="ClosesCase" Type="System.Boolean">True</Attribute>
> <Attribute Name="Description" Type="System.String">The case had no
sense
> and is no more active</Attribute>
> <Attribute Name="Name" Type="System.String">Closed</Attribute>
> </Entity>
> <Entity Type="EPT:Priority" Id="e23411d3-fc09-4ded-b6f1-95e22f7a0915">
> <Attribute Name="Name" Type="System.String">2 - Urgent</Attribute>
> </Entity>
> <Entity Type="EPT:State" Id="c62bbb33-1d43-4a5a-ad4d-8aabf16bf205">
> <Attribute Name="Name" Type="System.String">Resolved</Attribute>
> <Attribute Name="ClosesCase" Type="System.Boolean">True</Attribute>
> <Attribute Name="Description" Type="System.String">The case was
> solved</Attribute>
> </Entity>
> <Entity Type="EPT:Project" Id="adf6b7d7-96ef-4418-8028-5b7d7bbbc758">
> <Attribute Name="Name" Type="System.String">EUSS</Attribute>
> <Reference Role="Cases" RefId="230b2b34-8eb4-408e-a817-4c055525bafa"
/>
> <Reference Role="Cases" RefId="230b2b34-8eb4-408e-a817-4c055525bafa"
/>
> <Reference Role="Cases" RefId="230b2b34-8eb4-408e-a817-4c055525bafa"
/>
> </Entity>
> <Entity Type="EPT:Priority" Id="8743a910-aff9-4589-aab9-e849d68b90f6">
> <Attribute Name="Name" Type="System.String">Undefined</Attribute>
> </Entity>
> <Entity Type="EPT:Category" Id="166d7c81-b924-4022-83d3-829b6abbaf92">
> <Attribute Name="Bitmap"
> Type="System.String">~/images/app/feature.gif</Attribute>
> <Attribute Name="Name" Type="System.String">Feature</Attribute>
> </Entity>
> <Entity Type="EPT:Project" Id="243200bf-953f-4d25-a76e-644ac4ccd43f">
> <Attribute Name="Name" Type="System.String">Project
Tracker</Attribute>
> </Entity>
> <Entity Type="EPT:Category" Id="b5b5b603-9ca2-42a6-976e-8b1982f80ab6">
> <Attribute Name="Name" Type="System.String">Bug</Attribute>
> <Attribute Name="Bitmap"
> Type="System.String">~/images/app/bug.gif</Attribute>
> </Entity>
> <Entity Type="EPT:Priority" Id="6d127939-1b5b-4fe6-98e0-02ae6ea6bf57">
> <Attribute Name="Name" Type="System.String">Useless</Attribute>
> </Entity>
> <Entity Type="EPT:Case" Id="230b2b34-8eb4-408e-a817-4c055525bafa">
> <Attribute Name="Creation" Type="System.DateTime">4/27/2005 7:53:47
> PM</Attribute>
> <Attribute Name="Opened" Type="System.Boolean">True</Attribute>
> <Attribute Name="Description" Type="System.String">
> </Attribute>
> <Attribute Name="End" Type="System.DateTime">4/27/2005 12:00:00
> AM</Attribute>
> <Attribute Name="Category" Type="System.String">Feature</Attribute>
> <Attribute Name="Name" Type="System.String">New Case</Attribute>
> <Attribute Name="State" Type="System.String">Opened</Attribute>
> <Attribute Name="Priority" Type="System.String">Undefined</Attribute>
> </Entity>
> </USS>
>
> Thank you