Question

I am writing a function to update my XML and am having some issues. I’d hoped I could just set old XElement directly to the updated one but that doesn’t work in the foreach loop (though should only ever be one query result). I was going to hard-code each field, but then decided to use a loop. However when it hits the section and it’s sub-elements it reads it all as a single element and messed up the file

var myDevice = from c in appDataXml.Descendants("device")
               where (string)c.Element("name") == App.CurrentDeviceName 
                      && (string)c.Element("ip") == App.CurrentIp
               select c;

if (myDevice.Any())
{
    foreach (XElement device in myDevice)
    {
        //device.Element("customname").Value = updatedDevice.Element("customname").Value;

        for (int a = 0; a < device.Elements().Count(); a++)
        {
            string field = device.Elements().ElementAt(a).Name.ToString();
            device.Element(field).Value = updatedDevice.Element(field).Value;
        }
    }
}

sample XML

<Devices>
  <device>
    <name>blah</name>
    <customname>custom</customname>
    <ip>192.168.1.100</ip>
    <port>1000</port>
    <sources>
      <source>
        <code>00</code>
        <name>blah2</name>
        <hidden>False</hidden>
      </source>
      <source>
      ...etc
    </sources>
  </device>

Answer 1

You need to abstract (make classes) of your xml, it will help you CRUD and search it.

Example: (using these extensions: http://searisen.com/xmllib/extensions.wiki)

public class Device
{
    const bool ELEMENT = false;
    const bool ATTRIBUTE = true;

    XElement self;
    public Device(XElement self) { this.self = self; }

    public string CustomName 
    { 
        get { return self.Get("customname", string.Empty); }
        set { self.Set("customname", value, ELEMENT); }
    }
    public string Name { get { return self.Get("name", string.Empty); } }
    public string Ip { get { return self.Get("ip", "0.0.0.0"); } }
    public int Port { get { return self.Get("port", 0); } }

    public Source[] Sources
    {
        get { return _Sources ?? (_Sources = self.GetEnumerable("sources/source", xsource => new Source(xsource)).ToArray()); }
    }
    Source[] _Sources;

    public class Source
    {
        XElement self;
        public Source(XElement self) { this.self = self; }

        public string Code { get { return self.Get("code", string.Empty); } }
        public string Name { get { return self.Get("name", string.Empty); } }
        public bool Hidden { get { return self.Get("hidden", false); } }
    }
}

An example using it:

XElement xdevices = XElement.Load(file.FullName);
Device[] devices = xdevices.GetEnumerable("device", xdevice => new Device(xdevice)).ToArray();
var myDevice = devices
     .Where(d => d.Name == App.CurrentDeviceName 
              && d.Ip == App.CurrentIp);

foreach (Device device in myDevice)
{
    string name = device.Name;
    foreach (Device.Source source in device.Sources)
    {
        string sourceName = source.Name;
    }
    device.CustomName = "new name";
}
xdevices.Save(file.FullName);

It is a change in the way of thinking, so instead of worrying about how to reference a value, you create the class to read/write to the xml, and instead you just get/pass off data to a class, that then reads/writes the xml.

Edit:
—- Add to XElementConversions class —-

To be consistent with the file, and to work properly I made detailed versions. You can modify them to make the other types, like bool, DateTime, etc.

public static int GetInt(this XElement source, string name, int defaultValue)
{
    source = NameCheck(source, name, out name);
    return GetInt(source, source.GetDefaultNamespace() + name, defaultValue);
}

public static int GetInt(this XElement source, XName name, int defaultValue)
{
    int result;
    if (Int32.TryParse(GetString(source, name, null), out result))
        return result;
    return defaultValue;
}