There are four core objects that make up each .NET data provider:

• Connections - for connecting to and managing operations against a database.
• Commands - for issuing SQL commands to execute against a database.
• DataReaders - for directly reading data off a stream.
• DataSets and DataAdapters - for storing and manipulating data in a memory-resident data store.

The following diagram illustrates the components of the ADO.NET architecture.

In brief, the core ADO.NET functionalities may be summarized as follows:

1. A Connection object establishes the link between a Web page and a database.
2. Once a link exists, different forms of Commands can be issued to the database provider. Commands may either act directly against the database, or return a result set for further processing.
3. For fast, efficient display-only of data, the result set can be read by a DataReader.
4. To enable users to work with the data, the result set can be stored into a memory-resident DataSet object, which are manipulated via DataAdapter objects. Using the built-in methods in the DataAdapter, changes in the DataSet can easily be reconciled with the underlying data source.

Displaying Information from a Database