Question

I have two classes which need to be in same xml file. The way the classes are done mean I’m having to serialize separately. Which I have managed to do. The first I do using TextWriter.

TextWriter writer = new StreamWriter(filepath);
serializer.Serialize(writer, class, ns);

This works fine. Then I wanted to add another class to the file. So did same but added that I want to append not overwrite.

TextWriter writer = new StreamWriter(filepath, true);

This adds the new class to end but also adds another declaration so my XML file reads.

<?xml version="1.0" encoding"utf-8"?>
<dog>
...
</dog>
<?xml version="1.0" encoding"utf-8"?>
<cat>
...
</cat>

I’ve tried to use XmlWriter so I could use XmlWriterSettings then chose false for OmitXmlDeclaration but then it overrides the previous class I serialized.

Answer 1

Your XML needs a root element to be valid XML.

<?xml version="1.0" encoding"utf-8"?>
<animals>
    <dog/>
    <cat/>
<animals>

You could create a List<Animal> and serialize it. But if you do not have the same superclass, you can try to create a class like this:

[Serializable]
public class AnimalCollection : IXmlSerializable
{
    public void WriteXml(XmlWriter writer)
    {
        // Repeat for the Cat
        writer.WriteStartElement("Dog");

        XmlSerializer serializer = new XmlSerializer(TypeOf(Dog));
        using (StringWriter stringWriter = new StringWriter())
            {
                serializer.Serialize(stringWriter, _dog);
                string value = stringWriter.ToString();
                writer.WriteRaw(value);
            }

        writer.WriteEndElement();
    }
}

in the ReadXml and WriteXml you could use the generic serializer to serialize those objects then use the XmlWriter to write a startElement. endElement and include the serialized animal.