Saving Data To Xml

public class World
{
  public string Name;
  public Sphere[] Spheres;
}

public class Sphere
{
  public string Position;
}

a simple class structure.. now lets create a world with two spheres

World w = new World();
w.Name = "MyWorld";
w.Spheres = new Sphere[]{
  new Sphere(),new Sphere()
};
w.Spheres[0].Position = "Left";
w.Spheres[1].Position = "Right";

and now, we want to save this as xml.. how could we do that?

yes:

XmlSerializer ser = new XmlSerializer(typeof(World));
XmlTextWriter writer = new XmlTextWriter("World.xml",Encoding.Unicode);
writer.Formatting = Formatting.Indented; // we don't want it all in one line, do we?
ser.Serialize(writer,w);
writer.Close();

and the result? voilà:

<?xml version="1.0" encoding="utf-16"?>
<World xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
 <Name>MyWorld</Name>
 <Spheres>
  <Sphere>
   <Position>Left</Position>
  </Sphere>
  <Sphere>
   <Position>Right</Position>
  </Sphere>
 </Spheres>
</World>

you want the name and position as xml attribute instead? so add meta-attributes to your classes. like this:

public class World
{
  [XmlAttribute()]
  public string Name;
  public Sphere[] Spheres;
}

public class Sphere
{
  [XmlAttribute()]
  public string Position;
}

result:

<?xml version="1.0" encoding="utf-16"?>
<World xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" Name="MyWorld">
 <Spheres>
  <Sphere Position="Left" />
  <Sphere Position="Right" />
 </Spheres>
</World>

thats about it..

loading should be rather intuitive now, shouldn't it?

well.. what else do you need? exactly:

using System.Xml.Serialization;
using System.Xml;

and that was it. have fun!

okay.. i've played a bit with inheritance now, too.. here's what i got:


i added a subtype to sphere, namely sun

public class Sun : Sphere
{
  [XmlAttribute()]
  public string Shining;
}

and changed our second sphere to be a sun:

World w = new World();
w.Name = "MyWorld";
w.Spheres = new Sphere[]{
  new Sphere(),new Sun()
};
w.Spheres[0].Position = "Left";
w.Spheres[1].Position = "Right";
((Sun)w.Spheres[1]).Shining = "Bright";

and got an exception now. they are well documented (right in the exception), so i learned i have to include the type to the xml serializer.. so i did.. like that:

[XmlInclude(typeof(Sun))]
public class Sphere
{
  [XmlAttribute()]
  public string Position;
}

this tells that Sphere will possibly have a subclass of type Sun.

written that attribute, it compiles and runs fine.

hey... thank you for that !!!
i got the same exception yesterday at 11pm, after we talked about the stuff. i appears the exception doesn't turn up when you write inherited data, so i was confused and postponed the thing. i was to write a code snippet, too. well, maybe if i find out a few other cool things

i'm currently testing out other ways to collect the information on what inherited class types exist..

one way is to scan the array for it's types, and collect them, and pass as additional parameter to XmlSerializer.. like this:

static Type[] GetArrayTypes<T>(T[] array)
    {
      List<Type> types = new List<Type>();
      foreach (T item in array)
      {
        Type type = item.GetType();
        if (types.Contains(type) == false)
        {
          types.Add(type);
        }
      }
      Type[] collected = new Type[types.Count];
      for (int i = 0; i < types.Count; i++)
      {
        collected[i] = types[i];
      }
      return collected;
    }

(yeah, i know, a bit long, you can collect directly into an array, too, but you will have doubles/tribles, then.. wich i didn't wanted to).

a next thing, wich could be interesting, is to scan the whole World class, or possibly some type for all findable inherited classes.. with help of the reflection namespace..

if nothing else, i at least learn more about c# and the .NET framework, hehe

oh, and, generics rock!

What happens if you have a class like a graph?

public class Node
{
    internal ArrayList _edges;

...
}

public class Edge
{
    internal Node _nodeA;
    internal Node _nodeB;
...
}

public class Graph
{
    private ArrayList _nodes;
    private ArrayList _edges;
}

A node can - and usually is - connected to more than one edge. But AFAICT C# can't tell the difference between a reference and an instance, so If I serialize as illustrated above I get a f**ked up graph. (My custom serialiser converts node references to integer indices and saves these to get around this).

please don't resurrect old posts.