Serialize Class

The XmlSerializer is your new best friend when it comes to serializing objects to XML documents. It will save you from writing code using with the XmlDocument or XmlTextReader/-Writer classes to save and restore objects. Many of us are probably familiar developing serialization solutions using an XML parser directly, e.g. if you have an application sending the data over the internet. In your application, the data you want to send is lives encapsulated within objects, but you need to serialize the objects in order to send the data. You probably added boiler-pate code to these classes to persist fields to XML using a DOM Document class. If your application also received data in XML format you probably wrote more lines of boiler-plate code to parse the received XML and set the properties on your objects.

Now the XmlSerializer does it all for you. It handles the transformation both ways and, to make life even better, we do not even have to create the classes to serialize ourselves. If we have an XML schema describing the data layout of our transfer format we can generate .NET classes corresponding to the complex types in the schema with the Framework’s XSD schema definition tool. You can find all about the XSD tool in Appendix C. In the following sections of this chapter we will learn how to use the XmlSerializer, and how we need to design classes so the XmlSerializer can use them.

9.2.1 Round-trip serialization

Let’s start out developing a class for the XmlSerializer to process. The garage example document used throughout the first part of this book contained car element nodes with attributes to store some information about a car. That’s a good candidate for a class right there.

When we develop .NET classes we no longer need to worry about writing methods to serialize an object to XML. This functionality is built directly into the .NET Framework. Let’s start with a very simple

Car class. Each Car object needs members for make, model and the year the car was built.

Listing 9.1: example class to use with the XmlSerializer

public class Car

{

  public Car(){}

  public string Make;

  public string Model;

  public int Year;

}

This class is very straightforward, all the data stored is exposed through public fields. OK, exposing fields like this is generally bad design, but 1) this is an only example and 2) there is a reason why this example class declares its members public. We will hear more about that reason shortly. In chapters 12-14 we will also meet completely different approach to object serialization that in fact can serialize non-public members. Also notice that the class does not contain any methods or derive from any base classes to enable serialization.