How do I use XmlSerializer to handle different namespace versions?

Question

I am using the .NET XmlSerializer class to deserialize GPX files.

There are two versions of the GPX standard:

• <gpx xmlns="http://www.topografix.com/GPX/1/0"> ... </gpx>
• <gpx xmlns="http://www.topografix.com/GPX/1/1"> ... </gpx>

Also, some GPX files do not specify a default namespace:

• <gpx> ... </gpx>

My code needs to handle all three cases, but I can't work out how to get XmlSerializer to do it.

I am sure there must be a simple solution because this a common scenario, for example KML has the same issue.

Answer 1

I have done something similar to this a few times before, and this might be of use to you if you only have to deal with a small number of namespaces and you know them all beforehand. Create a simple inheritance hierarchy of classes, and add attributes to the different classes for the different namespaces. See the following code sample. If you run this program it gives the output:

Deserialized, type=XmlSerializerExample.GpxV1, data=1
Deserialized, type=XmlSerializerExample.GpxV2, data=2
Deserialized, type=XmlSerializerExample.Gpx, data=3

Here is the code:

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

[XmlRoot("gpx")]
public class Gpx {
        [XmlElement("data")] public int Data;
}

[XmlRoot("gpx", Namespace = "http://www.topografix.com/GPX/1/0")]
public class GpxV1 : Gpx {}

[XmlRoot("gpx", Namespace = "http://www.topografix.com/GPX/1/1")]
public class GpxV2 : Gpx {}

internal class Program {
    private static void Main() {
        var xmlExamples = new[] {
            "<gpx xmlns='http://www.topografix.com/GPX/1/0'><data>1</data></gpx>",
            "<gpx xmlns='http://www.topografix.com/GPX/1/1'><data>2</data></gpx>",
            "<gpx><data>3</data></gpx>",
        };

        var serializers = new[] {
            new XmlSerializer(typeof (Gpx)),
            new XmlSerializer(typeof (GpxV1)),
            new XmlSerializer(typeof (GpxV2)),
        };

        foreach (var xml in xmlExamples) {
            var textReader = new StringReader(xml);
            var xmlReader = XmlReader.Create(textReader);

            foreach (var serializer in serializers) {
                if (serializer.CanDeserialize(xmlReader)) {
                    var gpx = (Gpx)serializer.Deserialize(xmlReader);
                    Console.WriteLine("Deserialized, type={0}, data={1}", gpx.GetType(), gpx.Data);
                }
            }
        }
    }
}