How to find XmlNodes based on a child elements name and value

Question

Im having trouble getting a XmlNodeList where there is 1 child with a specific name that

<tables>
  <table tableName="Orders">
    <item table="Orders">
      ...
   </item>
    <item table="Orders">
      ...
   </item>
  </table>
  <table tableName="OrderWithParent">
    <item table="OrderWithParent">
      <column columnName="OrderWithParentId"><![CDATA[156]]></column>
      <column columnName="OrderParentId"><![CDATA[1]]></column>
      ...
   </item>
    <item table="OrderWithParent">
      <column columnName="OrderWithParentId"><![CDATA[156]]></column>
      <column columnName="OrderParentId"><![CDATA[1]]></column>
      ...
   </item>
    <item table="OrderWithParent">
      <column columnName="OrderWithParentId"><![CDATA[156]]></column>
      <column columnName="OrderParentId"><![CDATA[2]]></column>
      ...
   </item>
  </table>
</tables>

So thats my basic xml layout...

Ive deserialized the top Orders... and now i wanna find the OrderWithParent's where their column with columnName="OrderParentId" == order.Id

the order nodes where retrieved like this:

var orders = root.SelectNodes("/tables/table[@tableName='Orders']/item[@table='Orders']");

So atm im using an XmlDocument.. im hope to using XDocument aswell.. but i havent been able to find a solution with either of them. Help is much appreciated!

Answer 1

Assuming that order.Id means Id property of a predefined variable order which you didn't show, the following XPath should return the target item element :

var xpath = $"//item[@table='OrderWithParent' and column[@columnName='OrderWithParentId'] = {order.Id}]";

For older C# version where string interpolation $ is not supported :

var xpath = String.Format("//item[@table='OrderWithParent' and column[@columnName='OrderWithParentId'] = {0}]", order.Id);

Another assumption is, that order.Id value is always number. Otherwise you'll need to wrap the value with quotes in the XPath i.e in the above snippet, replace {order.Id} with '{order.Id}' or {0} with '{0}'.

If you switch to using XDocument, you can still execute the same XPath expression through XPathSelectElements(), XPathSelectElement(), or XPathEvaluate() methods.