ADO.NET Classes: Part 1
The following diagram displays the principal ADO.NET classes. The ADO.NET classes are organized into nested sets of collections. The principal class, DataSet, contains collections of DataTable and DataRelation instances. Each DataTable contains collections of DataColumn, DataRow, and Constraint instances. DataSet and its related classes are all members of the System.Data namespace.
Use DataSet to create a client-side cache of the data used by your application. With DataSet and its related classes, this cache can mimic many of the elements of a database. It can include: tables, rows, columns, relationships between tables, and constraints. Note that a single DataSet object can be filled with data from a variety of sources, including different databases, text, and XML files.