This appendix summarizes useful serialization topics and techniques.

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.

To serialize an object, follow these steps.

1. Create an XmlSerializer, passing its constructor the object’s type.
2. Create a TextWriter to hold the serialization.
3. Call the serializer’s Serialize method, passing it the TextWriter and the object to serialize.

The following code shows how a program might serialize a Customer object.

// Create a serializer that works with the Customer class.
XmlSerializer serializer = new XmlSerializer(typeof(Customer));

// Create a TextWriter to hold the serialization.
string serialization;
using (TextWriter writer = new StringWriter())
{
    // Serialize the Customer.
    serializer.Serialize(writer, customer);
    serialization = writer.ToString();
}

// Display the serialization.
serializationTextBox.Text = serialization;

To deserialize a serialization, follow these steps.

1. Create an XmlSerializer, passing its constructor the object’s type.
2. Create a TextReader from which to read the serialization.
3. Call the serializer’s Deserialize method, passing it the TextReader. Cast the result into the object’s type.

The following code shows how a program might deserialize a Customer object’s serialization.

// Create a serializer that works with the Customer class.
XmlSerializer serializer = new XmlSerializer(typeof(Customer));

// Create a stream from which to read the serialization.
using (TextReader reader = new StringReader(serialization))
{
    // Deserialize.
    Customer newCustomer = (Customer)serializer.Deserialize(reader);

    // Display the deserialization.
    DisplayCustomer(deserializedTextBox, newCustomer);
}

Controlling Serialization

The following table lists the most useful attributes that you can use to control serialization. (The names of the classes that implement these attributes all end with Attribute. For example, the first XmlArray attribute is implemented by the XmlArrayAttribute class. If you want to look up any of these online, use their full class names.)

The DataContractSerializer class can also use XML to serialize and deserialize objects. The process is similar to using the DataContractJsonSerializer class, which is summarized in the next section.

JSON Serialization

JavaScript Object Notation (JSON) is a data storage language that mostly consists of name:value pairs where names are text and values can have one of the following data types.

• Number
• String
• Boolean
• Array (a sequence of values separated by commas and enclosed in brackets [ ])
• Object (a collection of key:value pairs with pairs separated by commas and the whole collection surrounded by braces { })
• Null

The following section summarizes the basic JSON serialization and deserialization processes. The section after that describes attributes you can use to control the serialization.

Performing Serialization

The DataContractJsonSerializer class serializes and deserializes objects using the JSON format. The class’s WriteObject method serializes an object. Its ReadObject method deserializes an object.

The following code serializes and deserializes a Customer object in the JSON format.

// Create a serializer that works with the Customer class.
DataContractJsonSerializer serializer =
    new DataContractJsonSerializer(typeof(Customer)); 

// Create a stream to hold the serialization.
using (MemoryStream stream = new MemoryStream())
{
    // Serialize the Customer.
    serializer.WriteObject(stream, customer);

    // Convert the stream into a string.
    stream.Seek(0, SeekOrigin.Begin);
    string serialization;
    using (StreamReader reader = new StreamReader(stream))
    {
        serialization = reader.ReadToEnd();

        // Display the serialization.
        serializationTextBox.Text = serialization;

        // Deserialize from the stream.
        stream.Position = 0;
        Customer newCustomer = (Customer)serializer.ReadObject(stream);

        // Display the deserialization.
        DisplayCustomer(deserializedTextBox, newCustomer);
    }
}

Controlling Serialization

The following table lists attributes that are useful when performing JSON serializations.

Binary Serialization

The XML and JSON serializers cannot serialize some data types and cannot serialize a data structure that contains reference loops. However, the BinaryFormatter class can handle both of these issues.

The BinaryFormatter can work only with classes that are decorated with the Serializable attribute.

The following code shows how a program might use a BinaryFormatter to serialize and deserialize a Department object.

// Create a BinaryFormatter.
IFormatter formatter = new BinaryFormatter();

// Create a stream to hold the serialization.
using (MemoryStream stream = new MemoryStream())
{
    // Serialize.
    formatter.Serialize(stream, department);

    // Display a textual representation of the serialization.
    byte[] bytes = stream.ToArray();
    string serialization = BitConverter.ToString(bytes).Replace("-", " ");

    // Display the serialization.
    serializationTextBox.Text = serialization;

    // Deserialize.
    stream.Seek(0, SeekOrigin.Begin);
    Department newDepartment = (Department)formatter.Deserialize(stream);

    // Display the new Department's data.
    deserializedPictureBox.Image = newDepartment.Logo;
    deserializedTextBox.Text = DisplayDepartment(newDepartment);
}