Change Value of the last Attribute in an XML c#

Question

I was working on a bunch of XMLs that all share an attribute that contains the string "name" in them. The following code selects the attribute with string "name" in it and assign a new value to it.

        public void updateXmlFile(string strFileName)
    {
        try
        {
            //Load the Document
            XmlDocument doc = new XmlDocument();
            doc.Load(strFileName);
            //Set the changed Value
            string newValue = GetUniqueKey();
            //Select all nodes in the XML then choose from them
            //the first node that contain string "name" in it
            XmlNodeList list = doc.SelectNodes("//@*");
            XmlNode filteredNode = list.Cast<XmlNode>()
                .First(item => item.Name.ToLower().Contains("name"));
            //Assign the newValue to the value of the node
            filteredNode.Value = newValue;

            doc.Save(strFileName);
        }
        catch (XmlException xex) { Console.WriteLine(xex); }
    }

Now a new XMLs were added that dosen't have the string "name" in them, so instead of modifying the attribute with string "name" in it I decided to simply modify the last attribute no matter what it was (not the first)

Can anybody tell me how to do that?

EDIT

Here is an example of my XML

<?xml version="1.0" encoding="utf-8"?>
<CO_CallSignLists Version="24" ModDttm="2010-09-13T06:45:38.873" ModUser="EUADEV\SARE100" ModuleOwner="EUADEVS06\SS2008" CreateDttm="2009-11-05T10:19:31.583" CreateUser="EUADEV\A003893">
  <CoCallSignLists DataclassId="E3FC5E2D-FE84-492D-AD94-3ACCED870714" EntityId="E3FC5E2D-FE84-492D-AD94-3ACCED870714" MissionID="4CF71AB2-0D92-DE11-B5D1-000C46F3773D" BroadcastType="S" DeputyInSpecialList="1" SunSpots="1537634cb70c6d80">
    <CoCallSigns EntityId="DEBF1DDB-3C92-DE11-A280-000C46F377C4" CmdID="C45F3EF1-1292-DE11-B5D1-000C46F3773D" ModuleID="6CB497F3-AD63-43F1-ACAE-2C5C3B1D7F61" ListType="HS" Name="Reda Sabassi" Broadcast="INTO" PhysicalAddress="37" IsGS="1" HCId="0" CommonGeoPos="1" GeoLat="0.0000000" GeoLong="0.0000000">
      <CoRadios EntityId="E1BF1DDB-3C92-DE11-A280-000C46F377C4" RadioType="HF" />
    </CoCallSigns>
  </CoCallSignLists>
</CO_CallSignLists>

@Alex: You notice that the "SunSpots" attribute (last attribute in the first child element) is successfully changed. But now when I wanna load the XML back into the DB it gives me an error

Here is the modified code

    public void updateXmlFile(string strFileName)
    {
        try
        {
            XDocument doc = XDocument.Load(strFileName);

            XAttribute l_attr_1 = (doc.Elements().First().Elements().First().Attributes().Last());
            l_attr_1.Value = GetUniqueKey();

            Console.WriteLine("Name: {0}  Value:{1}", l_attr_1.Name, l_attr_1.Value);

            doc.Save(strFileName);
        }
        catch (XmlException xex) { Console.WriteLine(xex); }
    }

I was thinking of making an if statment which checks if the XML has an attribute that contains string "name" in it (since most of my XMLs has an attribute that contains name in them) if it does then change the attribute's value if not look for the last attribute and change it.. not the best solution but just throwing it out there

Answer 1

Look at class XmlAttributeCollection. You can get this collection by reading property Attributes of XmlNode. Just get the last by index.

Answer 2

Instead of .First(), use an extension method like this:

public static T LastOrDefault<T>(this IEnumerable<T> list)
{
  T val = null;
  foreach(T item in list)
  {
     val = item;
  }

  return val;
}

Answer 3

I've not tested this but you should be able to do all of this in the XPath expression. Something like this:

//@*[contains(node-name(.), 'name')][last()]

This will return only the last attribute with the string name anywhere in its name.

If you only want the last attribute, irrespective of it's name, use this:

//@*[last()]

Answer 4

Then definitely use Linq to XML. Example:

using System.Xml.Linq;

string xml = @"<?xml version=""1.0"" encoding=""utf-8""?>
<Commands Version=""439""  CreateUser=""Reda"">
  <CmCommands DataclassId=""57067ca8-ef96-4d2e-a085-6bd7e8b24126"" OrderName = ""Tea"" Remark=""Black"">
    <CmExecutions EntityId=""A9A5B0F2-6AB4-4619-9106-B0F85F86EE01"" Lock=""n"" />
  </CmCommands>
</Commands>";

XDocument x = XDocument.Parse(xml);

Debug.Print(x.Elements().First().Elements().First().Attributes().Last().Value);
//                 Commands ^      CmCommands ^             Remark ^

That is, word for word, the last attribute of the first child of the first element.

You can also query for element/attribute names, like:

Debug.Print(x.Descendants(XName.Get("CmCommands", "")).First().Attribute(XName.Get("Remark", "")).Value);

And of course you can use all of the Linq goodness like Where, Select, Any, All etc.

Note: replace XDocument.Parse with XDocument.Load if appropriate etc.