Question

I have to following XML file:

<root xmlns="http://someurl/element" xmlns:text="http://someurl/text">
   <elements>
     <element>
       <Id>text:SOME_ID</Id>
        <!-- some other elements -->
     </element>
      <element>
       <!-- some other elements -->
        <reference>
          <link ref="text:SOME_ID" />
        </reference>
     </element>
   </elements>
 </root>

I want to select all child elements of the elment node which have the element Id=text:SOME_ID, how can i get it using xmldocument method

Answer 1

From your question it is not entirely clear to me what you want to select but I assume you want to select <element> having child <Id> with content text:SOME_ID.

If you insist on using XmlDocument you can use it like this:

IEnumerable<XPathNavigator> GetElements(String xml, String id) {
  var xmlDocument = new XmlDocument();
  xmlDocument.LoadXml(xml);
  var namespaceManager = new XmlNamespaceManager(xmlDocument.NameTable);
  namespaceManager.AddNamespace("ns", "http://someurl/element");
  var navigator = xmlDocument.CreateNavigator();
  var xPath = "//ns:element/ns:Id[. = '" + id + "']/..";
  return navigator.Select(xPath, namespaceManager).Cast<XPathNavigator>();
}

However, I recommend using LINQ to XML:

IEnumerable<XElement> GetElements(String xml, String id) {
  XNamespace ns = "http://someurl/element";
  var xDocument = XDocument.Parse(xml);
  return xDocument
    .Descendants(ns + "element")
    .Where(element => (String) element.Element(ns + "Id") == id);
}