XmlReader.ReadContentAsObject always returns string type - windows-phone-7

Question

According to the MSDN documentation, XMLWriter.WriteValue writes xsd type information to the xml for simple CLR types. Then XMLReader.ReadContentAsObject supposedly reads out the appropriately-typed object when the XML is parsed. However, this always seems to return a string object for me and the ValueType property of the XMLReader is string. I've tried inserting longs and DateTimes, but they always end up as strings. Any ideas what I'm doing wrong or is this a Windows Phone bug?
XML Writing Code
public void WriteXml(XmlWriter writer) {
// KeyValuePair<string, object> pair initialized previously
writer.WriteStartElement(pair.Key);
writer.WriteValue(pair.Value)
writer.WriteEndElement();
}
XML Parsing Code
public void ReadXml(XMLReader reader) {
while (reader.Read()) {
if (reader.NodeType == XmlNodeType.Element) {
Type T = reader.ValueType; // T is string
reader.ReadStartElement();
object o = reader.ReadContentAsObject(); // o is string
o = reader.ReadContentAs(T, null); // o is string
}
}
}

Answer 1

You need to use a schema file (XSD) so that the framework can infer the type of a node. Otherwise ValueType will always return System.String.

Answer 2

MSDN says:
If a validation error occurs while parsing the content and the reader is an XmlReader object created by the Create method, the reader returns the content as a string. In other words when a validation error or warning occurs, the content is considered to be untyped.

Answer 3

I was making this too difficult. My goal was to serialize a Dictionary with generic type (string, object) by traversing its KeyValuePairs , but that class doesn't seem to be serializeable using XmlSerializer. I just created another class with two public properties, Key and Value, so I could use XmlSerializer. When deserializing with XmlSerializer, the type of Value is restored as long as it is a supported CLR type.
public void WriteXml(XmlWriter writer) {
// KeyValuePair<string, object> pair initialized previously
writer.WriteStartElement("entry");
MyClass toSerialize = new MyClass(pair.Key, pair.Value);
XmlSerializer serializer = new XmlSerializer(typeof(MyClass));
serializer.Serialize(writer, toSerialize);
writer.WriteEndElement();
}