Generic XmlSerializer

There are additional overloads of the XmlSerializer constructor that we have not discussed, but they merely offer different combinations of the parameters we just learned to use. One overload combines the functionality of all the other constructors: You can specify all the types the serializer can serialize, attach attributes to the types the serializer can handle, specify a root element name for each object the serializer reads or writes and define a default namespace:

XmlSerializer(Type type, XmlAttributeOverrides overrides,

  Type[] extraTypes, XmlRootAttribute root, string defaultNamespace);

One application of this overload is to create a generic serializer that can process many different root object types. Considering that instantiating an XmlSerializer object is an expensive operation, we can improve the performance of our applications by instantiating as few serializers as possible.

We can set up such a generic serializer by specifying the object type as the root type. The “real” types the constructor needs for setting up the serializer instance are all specified through the extraTypes parameter. Declaring object as the root type causes Serialize() to name the element for each object we pass in “anyType”. That’s hardly desirable because it does not map well to the real world, where the element names typically convey some information. To change the element names to something more descriptive we can either set the root parameter of the constructor, but this still only specifies one root element name for all serialized object graphs. Populating an XmlOverrides object, on the other hand, allows specifying a distinctive element name for each type we serialize. The following example for a constructor illustrates the concept of the generic serializer. This serializer instance can serialize, otherwise unrelated, string, int and Car objects and changes the root element name to “MyObject” for each type.

XmlSerializer serializer = new XmlSerializer( typeof(object),

  null, // XmlOverrides, use to customize root element names

  new Type[] { typeof(string), typeof(int), typeof(Car) },

  new XmlRootAttribute( "MyObject" ),

  null ); // XML namespace