Programming Visual Basic .NET

Managed Providers

When speaking of data access, it’s useful to distinguish between providers of data and consumers of data. A data provider encapsulates data and provides access to it in a generic way. The data itself can be in any form or location. For example, the data may be in a typical database management system such as SQL Server, or it may be distributed around the world and accessed via web services. The data provider shields the data consumer from having to know how to reach the data. In ADO.NET, data providers are referred to as managed providers .

A data consumer is an application that uses the services of a data provider for the purposes of storing, retrieving, and manipulating data. A customer-service application that manipulates a customer database is a typical example of a data consumer. To consume data, the application must know how to access one or more data providers.

ADO.NET is comprised of many classes, but five take center stage:

Connection

Represents a connection to a data source.

Command

Represents a query or a command that is to be executed by a data source.

DataSet

Represents data. The DataSet can be filled either from a data source (using a DataAdapter object) or dynamically.

DataAdapter

Used for filling a DataSet from a data source.

DataReader

Used for fast, efficient, forward-only reading of a data source.

With the exception of DataSet, these five names are not the actual classes used for accessing data sources. Each managed provider exposes classes ...