C# Xml Value always getting null

Question

I have the following Xml in my Resources.xmltest:

<?xml version="1.0" encoding="utf-8" ?>   
<Response xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://DFISofft.com/SmartPayments/">
    <Result>0</Result>
    <Message>Pending</Message>
    <PNRef>222131</PNRef>
    <ExtData>InvNum=123</ExtData>   
 </Response>

I've tried several ways to get the values, Result,Message,PNRef,ExtData, out of it and I've had no luck. I always get a null value for the NodePath so it never goes into the loop:

  var XmlDoc = new XmlDocument();

  XmlDoc.LoadXml(Resources.xmltest);
  XmlElement NodePath = (XmlElement) XmlDoc.SelectSingleNode("/Response");

  while (NodePath != null)
  {
    foreach (XmlNode Xml_Node in NodePath)
    {
      Console.WriteLine(Xml_Node.Name + " " + Xml_Node.InnerText);
    }
  }

I've tried this:

  XmlNode node3 = XmlDoc.SelectSingleNode("PNRef");
  Console.WriteLine(node3.Value);

  Console.WriteLine(XmlDoc.InnerXml);

  var tst = XmlDoc.GetElementsByTagName("PNRef");
  Console.WriteLine(tst);

And this:

  NodePath = (XmlElement) XmlDoc.SelectSingleNode("/Response");

  if (NodePath != null)
  {
    foreach (XmlNode node in NodePath)
    {
      Console.WriteLine("NodeName: " + Xml_NodeX.Name);
      Console.WriteLine("NodeValue: " + node.InnerText);
    }
   }

Apparently, I'm not getting the xml read/write. I've done it with DataSets but they do all the work for you.

Can someone point me in the right direction? I've been at this for longer than I should have been already.

Thank you!

Answer 1

Your XML has a XML namespace and you're not paying any attention to it:

<Response xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
          xmlns="http://DFISofft.com/SmartPayments/">
          ******************************************

When selecting from this XML, you need to use that XML namespace!

You're not taking into account the XML namespace (xmlns="http://nts-de-osm1-pxc/webservices/") on the document!

Try this:

 var XmlDoc = new XmlDocument();

 // setup the XML namespace manager
 XmlNamespaceManager mgr = new XmlNamespaceManager(XmlDoc.NameTable);

 // add the relevant namespaces to the XML namespace manager
 mgr.AddNamespace("ns", "http://DFISofft.com/SmartPayments/"); 

 XmlDoc.LoadXml(Resources.xmltest);

 // **USE** the XML anemspace in your XPath !!
 XmlElement NodePath = (XmlElement) XmlDoc.SelectSingleNode("/ns:Response");

  while (NodePath != null)
  {
    foreach (XmlNode Xml_Node in NodePath)
    {
      Console.WriteLine(Xml_Node.Name + " " + Xml_Node.InnerText);
    }
  }

Answer 2

The problem is your XPath query, which doesn't specify a namespace - despite the fact that your document only has a Response element in the "http://DFISofft.com/SmartPayments/" namespace. Ditto the PNRef elements.

Personally I'd use LINQ to XML if I actually wanted to use namespaces if at all possible. For example:

XNamespace ns = "http://DFISofft.com/SmartPayments/";
XDocument doc = XDocument.Load(filename);

foreach (var element in doc.Descendants(ns + "PNRef"))
{
    // Use element here
}

As you can see, LINQ to XML makes it really easy to use namespaces - but of course it requires .NET 3.5 or higher. If I had to use .NET 2.0, I'd either use XmlNamespaceManager or iterate manually and check local names instead of using XPath.