Chapter 9. ADO.NET XML Data Serialization

XML is the key element responsible for the greatly improved interoperability of the Microsoft ADO.NET object model when compared to Microsoft ActiveX Data Objects (ADO). In ADO, XML was merely an I/O format (nondefault) used to persist the contents of a disconnected recordset. The participation of XML in the building and in the interworkings of ADO.NET is much deeper. The aspects of ADO.NET in which the interaction and integration with XML is stronger can be summarized in two categories: object serialization and remoting and a dual programming interface.

In ADO.NET, you have several options for saving objects to, and restoring objects from, XML documents. In effect, this capability belongs to one object only—the DataSet object—but it can be extended to other container objects with minimal coding. Saving objects like DataTable and DataView to XML is essentially a special case of the DataSet object serialization.

As we saw in Chapter 8, ADO.NET and XML classes provide for a unified, intermediate API that is made available to programmers through a dual, synchronized programming interface—the XmlDataDocument class. You can access and update data using either the hierarchical node-based approach of XML or the relational approach of column-based tabular data sets. At any time, you can switch from a DataSet representation of the data to an XML Document Object Model (XML DOM) representation, and vice versa. Data is synchronized, and any change you enter in either model is immediately reflected and visible in the other.

In this chapter, we’ll explore the XML features built around the DataSet object and other ADO.NET objects for data serialization and deserialization. You’ll learn how to persist and restore data contents, how to deal with schema information, and even how schema information is automatically inferred from the XML source.