dot.NET.Framework.Essentials.1002003,.3Ed [Electronic resources] نسخه متنی

5.1 ADO.NET Architecture

Microsoft
ADO.NET's object
model encompasses two distinct groups of classes:
content
components and data-provider
components.[1] The content components include the
DataSet class
and other supporting classes, such as DataTable, DataRow, DataColumn, and
DataRelation. These classes contain the
actual content of a data exchange. The data-provider components
assist in data retrievals and updates. Developers can use the
connection, command, and data reader objects to directly
manipulate data. In more typical scenarios, developers use the
DataAdapter class as the conduit to move
data between the data store and the content components. The data can
be actual rows from a database or any other form of data, such as an
XML file or an Excel spreadsheet.

[1] In previous releases of this
book, we referred to the Data-Provider components as managed-provider
components.

Figure 5-1 shows the high-level architecture of
ADO.NET. ADO developers should have no problems understanding
connection and command objects. We offer a brief overview then go
into more detail in the rest of this chapter.

Figure 5-1. High-level architecture of ADO.NET

A data reader is a new object providing fast, forward-only, and
read-only access to data. This structure is similar to an ADO
Recordset, which has server-side, forward-only, and read-only cursor
types.

The DataSet class is analogous to a lightweight cache of a subset of
the database from the data store for disconnected operations. It also
allows reading and writing of data and schema in XML, and it is
tightly integrated with XmlDataDocument, as you will see later.

The DataAdapter class serves as a higher-level abstraction of the
connection and command classes. It enables you to load content from a
data store into a DataSet and reconcile DataSet changes back to the
data store.