Question

I’m having difficulty doing this seemingly simple task. I want to load XML files with the same ease of loading art assets:

        content  = new ContentManager(Services);
        content.RootDirectory = "Content";
        Texture2d background = content.Load<Texture2D>("images\\ice");

I’m not sure how to do this. This tutorial seems helpful, but how do I get a StorageDevice instance?

I do have something working now, but it feels pretty hacky:

public IDictionary<string, string> Get(string typeName)
        {
            IDictionary<String, String> result = new Dictionary<String, String>();
            xmlReader.Read(); // get past the XML declaration

            string element = null;
            string text = null;

            while (xmlReader.Read())
            {

                switch (xmlReader.NodeType)
                {
                    case XmlNodeType.Element:
                        element = xmlReader.Name;
                        break;
                    case XmlNodeType.Text:
                        text = xmlReader.Value;
                        break;
                }

                if (text != null && element != null)
                {
                    result[element] = text;
                    text = null;
                    element = null;
                }

            }
            return result;
        }

I apply this to the following XML file:

<?xml version="1.0" encoding="utf-8" ?>
<zombies>
  <zombie>
    <health>100</health>
    <positionX>23</positionX>
    <positionY>12</positionY>
    <speed>2</speed>
  </zombie>
</zombies>

And it is able to pass this unit test:

    internal virtual IPersistentState CreateIPersistentState(string fullpath)
    {
        IPersistentState target = new ReadWriteXML(File.Open(fullpath, FileMode.Open));
        return target;
    }

    /// <summary>
    ///A test for Get with one zombie.
    ///</summary>
    //[TestMethod()]
    public void SimpleGetTest()
    {
        string fullPath = "C:\\pathTo\\Data\\SavedZombies.xml";
        IPersistentState target = CreateIPersistentState(fullPath);
        string typeName = "zombie"; 

        IDictionary<string, string> expected = new Dictionary<string, string>();
        expected["health"] = "100";
        expected["positionX"] = "23";
        expected["positionY"] = "12";
        expected["speed"] = "2";

        IDictionary<string, string> actual = target.Get(typeName);

        foreach (KeyValuePair<string, string> entry in expected)
        {
            Assert.AreEqual(entry.Value, expected[entry.Key]);
        }
    }

Downsides to the current approach: file loading is done poorly, and matching keys to values seems like it’s way more effort than necessary. Also, I suspect this approach would fall apart with more than one entry in the XML.

I can’t imagine that this is the optimal implementation.

UPDATE: Following the advice of @Peter Lillevold, I’ve changed this a bit:

    public IDictionary<string, string> Get(string typeName)
    {
        IDictionary<String, String> result = new Dictionary<String, String>();

        IEnumerable<XElement> zombieValues = root.Element(@typeName).Elements();

        //result["health"] = zombie.Element("health").ToString();

        IDictionary<string, XElement> nameToElement = zombieValues.ToDictionary(element => element.Name.ToString());

        foreach (KeyValuePair<string, XElement> entry in nameToElement)
        {
            result[entry.Key] = entry.Value.FirstNode.ToString();
        }

        return result;
    }

    public ReadWriteXML(string uri)
    {
        root = XElement.Load(uri);
    }

    internal virtual IPersistentState CreateIPersistentState(string fullpath)
    {
        return new ReadWriteXML(fullpath);
    }

    /// <summary>
    ///A test for Get with one zombie.
    ///</summary>
    [TestMethod()]
    public void SimpleGetTest()
    {
        IPersistentState target = CreateIPersistentState("../../../path/Data/SavedZombies.xml");
        string typeName = "zombie"; 

        IDictionary<string, string> expected = new Dictionary<string, string>();
        expected["health"] = "100";
        expected["positionX"] = "23";
        expected["positionY"] = "12";
        expected["speed"] = "2";

        IDictionary<string, string> actual = target.Get(typeName);

        foreach (KeyValuePair<string, string> entry in expected)
        {
            Assert.AreEqual(entry.Value, actual[entry.Key]);
        }
    }

The loading is still pretty crappy, and somehow I wasn’t able to get the one-line ToDictionary to work with those two lambdas. I had to resort to that foreach loop. What am I doing wrong there?

Answer 1

There is also the new and shiny XElement (which sports Linq to XML). This sample will load an xml file, look up the zombie and dump the values into a dictionary:

var doc = XElement.Load("filename");
var zombieValues = doc.Element("zombie").Elements();
var zombieDictionary = 
    zombieValues.ToDictionary(
        element => element.Name.ToString(), 
        element => element.Value);

If you’d rather pick each value explicitly (and use casting for automatically converting into proper value types) you can do:

var zombie = doc.Element("zombie");
var health = (int)zombie.Element("health");
var positionX = (int)zombie.Element("positionX");
var positionY = (int)zombie.Element("positionY");
var speed = (int)zombie.Element("speed");

Update: fixing some typos and cleaning up a bit, your Get method should look like this:

public IDictionary<string, string> Get(string typeName)
{
    var zombie = root.Element(typeName);
    return zombie.Elements()
          .ToDictionary(
                  element => element.Name.ToString(),
                  element => element.Value);
}