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Linq to Xml get elementat
Sorry for the long XML sample below. The XML sample below has two records and each record has three similar Nodes (<datafield tag="500") What I want to accomplish is get the value of the second Node <datafield tag = “5000”>. The fallowing code I gets the value for all three nodes but I want something like get elementat(1). Appreciate your help.
I tried this but it didn’t worked MsgBox(xEle.Elements.ElementAt(1).Value)

Dim xd As XDocument = XDocument.Load("C:\Users\stopete\Desktop\Marc_conv ertxml.xml")
If xd IsNot Nothing Then
Dim datafields = From datafield In xd.Descendants("datafield")
Where (datafield.Attribute("tag").Value = "500")
Select datafield
For Each xEle In datafields
MsgBox(xEle)
Next
End If


XML
<?xml version="1.0"?>
<collection>
    <record>
        <leader>03799cam 2200493Ia 4500</leader>
        <controlfield tag="001">
            648168072
            <subfield code="a">Battle, Stephen L.</subfield>
        </controlfield>
        <controlfield tag="003">SIRSI</controlfield>
        <controlfield tag="005">20110207150903.0</controlfield>
        <controlfield tag="008">100716s2010 caub bm f000 0 eng d</controlfield>
        <controlfield tag="007">cr b|||||a||||</controlfield>
        <datafield tag="035" ind1=" " ind2=" ">
            <subfield code="a">AD#</subfield>
            <subfield code="c">AD#</subfield>
            <subfield code="d">AD#</subfield>
        </datafield>
        <datafield tag="037" ind1=" " ind2=" ">
            <subfield code="a">hey</subfield>
        </datafield>
        <datafield tag="040" ind1=" " ind2=" ">
            <subfield code="a">ADA524509</subfield>
            <subfield code="b">DTI</subfield>
        </datafield>
        <datafield tag="043" ind1=" " ind2=" ">
            <subfield code="a">n-us---</subfield>
        </datafield>
        <datafield tag="049" ind1=" " ind2=" ">
            <subfield code="a">AD#A</subfield>
        </datafield>
        <datafield tag="100" ind1="1" ind2=" ">
            <subfield code="a">Battle, Stephen L.</subfield>
        </datafield>
        <datafield tag="245" ind1="1" ind2="0">
            <subfield code="a">Lessons in legitimacy</subfield>
            <subfield code="h">[electronic resource] :</subfield>
            <subfield code="b">the LTTE end-game of 2007--2009 /</subfield>
            <subfield code="c">Stephen L. Battle.</subfield>
        </datafield>
        <datafield tag="260" ind1=" " ind2=" ">
            <subfield code="a">Monterey, California :</subfield>
            <subfield code="b">Naval Postgraduate School,</subfield>
            <subfield code="c">2010.</subfield>
        </datafield>
        <datafield tag="300" ind1=" " ind2=" ">
            <subfield code="a">xiv, 57 p. :</subfield>
            <subfield code="b">ill. (1 col map) ;</subfield>
            <subfield code="c">28 cm.</subfield>
        </datafield>
        <datafield tag="500">
            <subfield code="a">Thesis Advisor(s): Borer, Douglas A. ; Second Reader: Chatterjee, Anshu.</subfield>
        </datafield>
        <datafield tag="500">
            <subfield code="a">"June 2010."</subfield>
        </datafield>
        <datafield tag="500">
            <subfield code="a">Author(s) subject terms: LTTE, Counter Insurgency, COIN, Sri Lanka, Tamil Eelam, Eelam War IV, SLAF, South Asia.</subfield>
        </datafield>
    </record>
    <record>
        <leader>02919cam 2200493Ia 4500</leader>
        <controlfield tag="001">648167554</controlfield>
        <controlfield tag="003">SIRSI</controlfield>
        <controlfield tag="005">20110207150310.0</controlfield>
        <controlfield tag="008">100716s2010 caua bm f000 0 eng d</controlfield>
        <controlfield tag="007">cr b|||||a||||</controlfield>
        <datafield tag="035" ind1=" " ind2=" ">
            <subfield code="a">AD#</subfield>
            <subfield code="c">AD#</subfield>
            <subfield code="d">AD#</subfield>
        </datafield>
        <datafield tag="037" ind1=" " ind2=" ">
            <subfield code="a">hey</subfield>
        </datafield>
        <datafield tag="040" ind1=" " ind2=" ">
            <subfield code="a">ADA524541</subfield>
            <subfield code="b">DTI</subfield>
        </datafield>
        <datafield tag="043" ind1=" " ind2=" ">
            <subfield code="a">n-us---</subfield>
        </datafield>
        <datafield tag="049" ind1=" " ind2=" ">
            <subfield code="a">AD#A</subfield>
        </datafield>
        <datafield tag="100" ind1="1" ind2=" ">
            <subfield code="a">Battaglia, Neal F.</subfield>
        </datafield>
        <datafield tag="245" ind1="1" ind2="0">
            <subfield code="a">Utility of satellite LIDAR waveform data in shallow water</subfield>
            <subfield code="h">[electronic resource] /</subfield>
            <subfield code="c">Neal F. Battaglia.</subfield>
        </datafield>
        <datafield tag="260" ind1=" " ind2=" ">
            <subfield code="a">Monterey, California :</subfield>
            <subfield code="b">Naval Postgraduate School,</subfield>
            <subfield code="c">2010.</subfield>
        </datafield>
        <datafield tag="300" ind1=" " ind2=" ">
            <subfield code="a">xvi, 67 p. :</subfield>
            <subfield code="b">ill. (some col.) ;</subfield>
            <subfield code="c">28 cm.</subfield>
        </datafield>
        <datafield tag="500">
            <subfield code="a">Thesis Advisor(s): Olsen, Richard C. ; Second Reader: Trask, David M.</subfield>
        </datafield>
        <datafield tag="500">
            <subfield code="a">"June 2010."</subfield>
        </datafield>
        <datafield tag="500">"
            <subfield code="a">Author(s) subject terms: LIDAR Waveforms, Underwater LIDAR signature, Spaceborne LIDAR.</subfield>
        </datafield>
    </record>
</collection>
Posted
Updated 15-Apr-11 6:45am
v3

You could Skip the first element if you want the second one specifically like this:

<code>
 Dim datafields = (From datafield In xd.Descendants("datafield")    Where (datafield.Attribute("tag").Value = "500")    Select datafield).Skip(1).First()
</code>


Additionally you could skip as many items as you like, not just the first one.
Hope this helped :) Good luck
 
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Comments
stopete82 15-Apr-11 13:36pm    
Thanks for the quick response. With your help I think I am in the right track. However; the sample you send I get the right output for the first record but then it doesn't go to next record. Do you know what I need to add to go to the next record?

Code:

Dim xd As XDocument = XDocument.Load("C:\Users\stopete\Desktop\Marc_convertxml.xml")
If xd IsNot Nothing Then

Dim datafields = (From datafield In xd.Descendants("datafield")
Where (datafield.Attribute("tag").Value = "500")
Select datafield).Skip(0).First()


For Each xEle In datafields.Elements

MsgBox(xEle)

Next

End If

Ouput:

Thesis Advisor(s): Borer, Douglas A. ; Second Reader: Chatterjee, Anshu.



Disire output:

First record
Thesis Advisor(s): Borer, Douglas A. ; Second Reader: Chatterjee, Anshu.

Second record
Thesis Advisor(s): Olsen, Richard C. ; Second Reader: Trask, David M.


Thanks for all your help.
mario_silent 15-Apr-11 14:19pm    
Ok here you go. First we get the XElements of the records, and loop through them to select the tag with attribute == 500. This should display in your test xml both records:
<pre>

var records = (from datafields in xd.Descendants("record") select datafields);
foreach (XElement e in records)
{
var data = (from datafield in e.Descendants("datafield")
where (datafield.Attribute("tag").Value == "500")
select datafield).Skip(0).First();
Console.WriteLine(data.Value);
}

</pre>

SOrry if it's in c# but it shouldn't be a problem to translate to VB, just a few tweaks :) Hope this helps
stopete82 15-Apr-11 17:43pm    
Sorry, for some reason I didn't see your code. However, I converted the code to VB.net but I get a syntax error Variable 'e' hides a variable in an enclosing block. Maybe somebody can see what I am missing in code. Apprciate your help.

Code:

Dim xd As XDocument = XDocument.Load("C:\Users\stopete\Desktop\Marc_convertxml.xml")

Dim records = (From datafields In xd.Descendants("record")
Select datafields)


For Each e As XElement In records
Dim data = (From datafield In e.Descendants("datafield") Where (datafield.Attribute("tag").Value = "500")
Select datafield).Skip(0).First()
MsgBox(data.Value)
Next

mario_silent 15-Apr-11 17:47pm    
I think you can ommit the e as XElement and just leave for each e In records like you had done previously
stopete82 15-Apr-11 14:34pm    
Thanks for the reply Skip(0) works it gives me the right result for the first record. However; the problem now is that it stops at first record, do you know what I need to add so it will traverse the whole xml document.
You can also you an XPath expression in LINQ.
Here is how it can be done :


VB
Dim datafields = (From datafield in xd.XPathSelectElement("//datafield[@tag='500' and position()=2]") _
select datafield)


It will return a single element of Type XElement.
 
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