.NET & XML

Manipulating Data Offline

Despite all these classes, there are times when you won’t want to write SQL for every database operation, and you’ll want to be able to manipulate entire sets of data as a whole without maintaining an open database connection. The mechanism for such operations is the DataSet.

A DataSet is an in-memory representation of a database. Just as a database contains tables, a DataSet contains a DataTableCollection (a collection of DataTable objects). Just as tables are related to one another, a DataSet contains a DataRelationCollection (a collection of DataRelation objects). Each DataTable contains a DataColumnCollection, which represents the table’s columns, and a DataRowCollection, which represents the table’s rows. The DataTable also contains references to various DataRelation and Constraint objects, which reflect the underlying table’s relations and constraints. You can create a DataSet from scratch and fill it with data, or you can use an IDbDataAdapter to map a DataSet to a database.

Figure 11-2 shows the structure of the DataSet class and its related classes.

Figure 11-2. The DataSet object model

Here’s where the talk about the databases meets the subject of this book, XML. You can serialize the data and structure of a DataSet to XML. You can generate a DataSet subclass from an XML Schema. You can read data from a DataSet as if it were an XML document. ...