Develop Reference

How to Get XML Element by It's 'Value' using XML C# SDK

I have this snippt of XML
<unit class="xxx.xxx.xxx" id="382">
<customId>000</customId>
<description>kg</description>
<key>22452</key>
<Description>Kilogramm</Description>
</unit>
how to get the node 'unit' or parnet of the key element using the value of an element. For instance
i have the value of key element above [22452] and it's Uniqe inside the xml-File.
what i am trying to do getting value of customid [000] of that specific tag.
what i did:
var doc = new XmlDocument();
doc.Load(stream); // stream from xml-file
var key = doc.SelectSingleNode(//key/[text()='" + 22452+ "']"); // that i am not sure about it.
var customId = key.InnerText("customId");

For this kind of query you could either find the node and than navigate to the parent.
Or use XPath:
var unitElemnt = doc.SelectSingleNode("//unit[key = '22452']");
(Assuming I've remembered the XPath to match an element's text content correctly.)
This gets a reference to the <unit> element, by using a relative path to the <key> element in the predicate of the XPath expression.
Generally better to avoid // in XPath for performance, but would need full document structure to do that.

For this you can use Linq to Xml queries.
XElement units = XElement.Load("./Test.xml");
XElement unit = (from item in units.Descendants("unit")
where item.Element("key").Value == "22455"
select item).FirstOrDefault();
string customId = unit.Element("customId").Value;
supposing your xml file look like :
<?xml version="1.0" encoding="utf-8"?>
<units>
<unit class="xxx.xxx.xxx" id="385">
<customId>003</customId>
<description>kg</description>
<key>22455</key>
<Description>Kilogramm</Description>
</unit>
<unit class="xxx.xxx.xxx" id="386">
<customId>004</customId>
<description>kg</description>
<key>22456</key>
<Description>Kilogramm</Description>
</unit>
</units>
for more reading check Microsoft Linq to Xml Docs

Why xmlDocument.Select return zero count

i am trying to access a node for xml
<?xml version="1.0" encoding="utf-8"?>
<LinkAnalysis>
<ImgInfo>
<Number>xyz</Number>
<ImgPath>D:\Projects\VERBALinks\VERBALinks\bin\Debug\LA_img\xyz.png</ImgPath>
</ImgInfo>
</LinkAnalysis>
using following code
var nodes = doc.SelectNodes(String.Format("/LinkAnalysis/ImgInfo[#Number=\"{0}\"]", "xyz"));
But it returns me zero count. Why??

<Number> is an element, not an attribute, so your XPath expression is wrong.
Try:
String.Format("/LinkAnalysis/ImgInfo[Number/text()='{0}']", "xyz")

Modify Node Value C# with ID

Here is my XML :
<?xml version="1.0" encoding="utf-8" ?>
<Selection>
<ID>1</ID>
<Nom>Name 1</Nom>
<DateReference>0</DateReference>
<PrefixeMedia>Department</PrefixeMedia>
<FormatExport>1630</FormatExport>
<TraceAuto>Oui</TraceAuto>
<SubID></SubID>
</Selection>
<Selection>
<ID>2</ID>
<Nom>Name 1</Nom>
<DateReference>0</DateReference>
<PrefixeMedia>Department</PrefixeMedia>
<FormatExport>1630</FormatExport>
<TraceAuto>1</TraceAuto>
<SubID>1</SubID>
</Selection>
My problem is I would like to modify for example the node content of <Nom>Name 1</Nom> which is located in <Selection></Selection> which have <ID>1</ID> (Search by ID)
I'm using XElement and XDocument to do simple search but I need some help to solve this problem above. (Developpment on SilverLight
Best Regards.

Another way to do this is using XmlDocument:
XmlDocument xmlDoc = new XmlDocument();
xmlDoc.Load(#"\path\to\file.xml");
// Select the <nom> node under the <Selection> node which has <ID> of '1'
XmlNode name = xmlDoc.SelectSingleNode("/Selection[ID='1']/Nom");
// Modify the value of the node
name.InnerText = "New Name 1";
// Save the XML document
xmlDoc.Save(#"\path\to\file.xml");

If you don't know how to get at the correct <Nom> node to update, the trick is to first select a <Selection> node that contains the correct <ID> node, then you can get that <Nom> node.
Something like:
XElement tree = <your XML>;
XElement selection = tree.Descendants("Selection")
.Where(n => n.Descendants("ID").First().Value == "1") // search for <ID>1</ID>
.FirstOrDefault();
if (selection != null)
{
XElement nom = selection.Descendants("Nom").First();
nom.Value = "Name one";
}
Note 1: By using Descendants("ID").First() I expect every Selection node to contain an ID node.
Note 2: And every Selection node contains a Nom node
Note 3: Now you still have to store the whole XML, if that's what you need.

XDocument.XPathSelectElements : I can't seem get the xpath syntax right

I'm trying to work out why my xpath won't select the nodes I specificy
My xpath expression is //DefaultValue, so I expect all elements of name DefaultValue to be selected
My test file (cut down) is :
<?xml version="1.0" encoding="utf-8"?>
<SharedDataSet xmlns:rd="http://schemas.microsoft.com/SQLServer/reporting/reportdesigner" xmlns="http://schemas.microsoft.com/sqlserver/reporting/2010/01/shareddatasetdefinition">
<Description />
<DataSet Name="ddd">
<Query>
<DataSourceReference>xxx</DataSourceReference>
<DataSetParameters>
<DataSetParameter Name="p1">
<DefaultValue>baaaah</DefaultValue> <!-- this node should be selected eh? -->
</DataSetParameter>
<DataSetParameter Name="p2">
<DefaultValue>fooo</DefaultValue> <!-- this node should be selected too eh? -->
</DataSetParameter>
</DataSetParameters>
</Query>
</SharedDataSet>
Code is :
XmlNamespaceManager xn = new XmlNamespaceManager(new NameTable());
xn.AddNamespace("ns", "http://schemas.microsoft.com/sqlserver/reporting/2010/01/shareddatasetdefinition");
xn.AddNamespace("rd", "http://schemas.microsoft.com/SQLServer/reporting/reportdesigner");
xn.AddNamespace("cl", "http://schemas.microsoft.com/sqlserver/reporting/2010/01/componentdefinition");
XDocument document = XDocument.Parse(reportBuffer, LoadOptions.PreserveWhitespace);
IEnumerable<XElement> elements = document.XPathSelectElements(xpath, xn);
at this point elements.Count() equals 0
Can anyone see what foolishness I present?
I can't seem to make the xml demons happy... :-(

The <DefaultValue> element is actually bound to the namespace http://schemas.microsoft.com/sqlserver/reporting/2010/01/shareddatasetdefinition.
The <SharedDataSet> document element has it declared without a prefix, so it is easy to miss. Since <DefaultValue> is a descendant, it inherits the namespace.
If you want to select the <DefaultValue> element you need to adjust your XPath:
//ns:DefaultValue

XmlNode.SelectSingleNode returns element outside current?

my problem is like this. Let's say i have xml like this
<root>
<child Name = "child1">
<element1>Value1</element1>
<element2>Value2</element2>
</child>
<child Name = "child2">
<element1>Value1</element1>
<element2>Value2</element2>
<element3>Value3</element3>
</child>
</root>
I have a method that gets as parameter XmlNode "node". Lets say "node" has value "child1" Then i try like this:
node.SelectSingleNode( "//element3" );
The problem is this code returns element3 from "child2". What i want is if there is no child "element3" of "node" to return null so i add it by hand.
Best Regards,
Iordand

The XPath expression you have isn't what you want.
Replace it with this:
node.SelectSingleNode( "element3" );
And you'll get the result you're looking for.

The following work perfect when i want to run xpath on the specified node.
XmlNodeList nodes = xmlDoc.SelectNodes(".//Child");

The "//" is a global look up.
What you'll need to do is get a list of all children
XmlNodeList nodes = xmlDoc.SelectNodes("//Child");
loop through that list and do a
XmlNode node = nodes.SelectSingleNode("element3");
This will return null if it's not there, and will step through every child looking.

the problem here is the XPath expression you are using, try it without the '//'. Like that:
node.SelectSingleNode( "element3" );
Read more here .