C# 4 and .NET 4

934 ❘ ChaPTer 33 mAnipulAtinG xml
Looking at the list box, you can check that in the data tables that were created all the columns have the
correct names and data types.
Something else you might want to note is that, because the previous two examples did not transfer any data
to or from a database, no SqlDataAdapter or SqlConnection was defi ned. This shows the real fl exibility
of both the System.Xml namespace and ADO.NET: you can look at the same data in multiple formats.
If you need to do a transform and show the data in HTML format, or if you need to bind the data to a grid,
you can take the same data and, with just a method call, have it in the required format.
serializing objeCTs in Xml
Serializing is the process of persisting an object to disk. Another part of your application, or even a separate
application, can deserialize the object, and it will be in the same state it was in prior to serialization. The
.NET Framework includes a couple of ways to do this.
This section looks at the System.Xml.Serialization namespace, which contains classes used to serialize
objects into XML documents or streams. This means that an object ’ s public properties and public fi elds are
converted into XML elements, attributes, or both.
The most important class in the System.Xml.Serialization namespace is XmlSerializer . To serialize
an object, you fi rst need to instantiate an XmlSerializer object, specifying the type of the object to
serialize. Then you need to instantiate a stream/writer object to write the fi le to a stream/document. The
fi n a l s t ep i s to c a l l t he Serialize() method on the XMLSerializer , passing it the stream/writer object and
the object to serialize.
Data that can be serialized can be primitive types, fi elds, arrays, and embedded XML in the form of
XmlElement and XmlAttribute objects.
To deserialize an object from an XML document, you reverse the process in the previous example.
You create a stream/reader and an XmlSerializer object and then pass the stream/reader to the
Deserialize() method. This method returns the deserialized object, although it needs to be cast to
the correct type.
The XML serializer cannot convert private data, only public data, and it cannot
serialize object graphs. However, these should not be serious limitations; by carefully
designing your classes, you should be able to easily avoid these issues. If you do need to
be able to serialize public and private data as well as an object graph containing many
nested objects, you will want to use the System.Runtime.Serialization
.Formatters.Binary namespace.
Some of the other tasks that you can accomplish with System.Xml.Serialization classes are:
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Determine if the data should be an attribute or element
Specify the namespace
Change the attribute or element name
The links between your object and the XML document are the custom C# attributes that annotate your
classes. These attributes are what are used to inform the serializer how to write out the data. The xsd.exe
tool, which is included with the .NET Framework, can help create these attributes for you. xsd.exe can do
the following:
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Generate an XML schema from an XDR schema fi le
Generate an XML schema from an XML fi le
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