C# 5.0 Programmer's Reference

564 ❘ CHAPTER 25 Serialization
This chapter explains serialization. It explains how to serialize and deserialize objects. It also
explains attributes that you can use to control how objects of a particular class are serialized.
The .NET Framework gives you three choices for how data is stored in a serialization: XML data,
JSON data, or binary data. The following sections explain how you can use each of these three choices.
Serialization Namespaces
The System.Xml.Serialization namespace includes XML serialization classes.
To make that kind of serialization easier, you may want to include the following
using directive in your code.
using System.Xml.Serialization;
The System.Runtime.Serialization.Json namespace includes JSON serialization
classes. To make that kind of serialization easier, you may want to include the
following using directive in your code.
using System.Runtime.Serialization.Json;
The JSON classes are included in the System.ServiceModel.Web library. If you
will be using those classes, use Project ➪ Add Reference to add a reference to that
library to your project.
XML Serialization
To serialize and deserialize objects in XML format, you use the XmlSerializer class’s Serialize
and Deserialize methods. The methods work only for classes that have a parameterless constructor,
either the default constructor or one that you created. They also work only for public properties
and fields. All other properties and fields are ignored.
Why a Parameterless Constructor
If you think about it, you’ll realize why serialization has these restrictions. To serialize
an object, the serializer must get an object’s property and field values. If a property or
field is not public, the serializer cannot see it.
When you deserialize an object, the serializer must create a new object and then set its
values. If the class doesn’t have a parameterless constructor, it would need some way
to figure out which constructor to use and what values to pass into it. You might cook
up some scheme for telling it which constructor to use and how, but it would make
deserialization more complicated. It’s just easier to require a parameterless constructor.
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