Question

I am writing some code to parse an xml file of the following format (truncated for simplicity)

<?xml version="1.0" encoding="UTF-8"?>
<ship name="Foo">
 <base_type>Foo</base_type>
 <GFX>fooGFX</GFX>
 ....
</ship>

I am using a dictionary consisting of key pairs of parameter and and xpath to value, and querying this to load all the values into various variables. However, I am noticing that there will be a massive amount of code duplication. In fact, for every value I wish to retrieve, I will have to write another line of almost identical looking code. Here is my code:

class Ship
{
    public Ship()
    {
        paths = new Dictionary<string, string>();
        doc = new XmlDocument();
        //Define path to various elements
        paths.Add("name", "/ship/@name");
        paths.Add("base_type", "/ship/base_type");
        paths.Add("GFX", "/ship/GFX");
    }
    public void LoadFile(string filename)
    {// Loads the file and grabs the parameters
        doc.Load(filename);
        Name = doc.SelectSingleNode(paths["name"]).Value;
        Base_type = doc.SelectSingleNode(paths["base_type"]).Value;
        GFX = doc.SelectSingleNode(paths["GFX"]).Value;
    }

    public Dictionary<string, string> paths; //The XPaths to the various elements, define them in constructor
    public XmlDocument doc;
    public string Name;
    public string Base_type;
    public string GFX;
}

Notice the duplication here:

variable = doc.SelectSingleNode(paths["variable_name"]).value. 

There are going to be many more variables, so this section will be massive.

Is there anyway to simplify this? If this was C++, I would probably try pointers, but I know they are not recommended for use in C#, so is there a similar way?

I would be looking for something that I could give a list of variable names and xpaths, and have the code pull out all the values and load them in the variable in some kind of loop or something. I want to use XPaths because I expect that the format of this file may change periodically.

Any ideas?

Thanks in advance.

EDIT: I would also like to be able to modify this data and save it back. I am not adverse to saving an entire new tree if necessary, but it would be nice to modify the data in place if possible. I don’t need a solution for the modification, but I just need to have this option open.

Answer 1

One good way to achieve the population of the object is by using XmlSerializer.Deserialize().

Something like this:

namespace TestSerialization
{
    using System;
    using System.IO;
    using System.Xml;
    using System.Xml.Serialization;

    public class TestSerialization
    {
        static void Main(string[] args)
        {
            string theXml =
@"<ship name='Foo'>
 <base_type>Foo</base_type>
 <GFX>fooGFX</GFX>
</ship>";
            Ship s = Ship.Create(theXml);

            // Write out the properties of the object.
            Console.Write(s.Name + "\t" + s.GFX);
        }
    }

    [XmlRoot("ship")]
    public class Ship
    {
        public Ship() { }

        public static Ship Create(string xmlText)
        {
            // Create an instance of the XmlSerializer specifying type.
            XmlSerializer serializer = new XmlSerializer(typeof(Ship));

            StringReader sr = new StringReader(xmlText);

            XmlReader xreader = new XmlTextReader(sr);

            // Use the Deserialize method to restore the object's state.
            return (Ship)serializer.Deserialize(xreader);
        }

        [XmlAttribute("name")]
        public string Name;

        [XmlElement("base_type")]
        public string Base_type;

        public string GFX;
    }
}

UPDATE: The OP has added an additional question:

I would also like to be able to modify this data and save it back. I
am not adverse to saving an entire new tree if necessary

Just use the XmlSerializer.Serialize() method.

Here is a typical example of using it:

  // Create an XmlTextWriter using a FileStream.
  Stream fs = new FileStream(filename, FileMode.Create);
  XmlWriter writer = 
  new XmlTextWriter(fs, Encoding.Unicode);
  // Serialize using the XmlTextWriter.
  serializer.Serialize(writer, yourObject);
  writer.Close();