Name
DataAdapter
Synopsis
DataAdapter classes are provider-specific types
that act as a bridge between a data source (such as a SQL Server
database) and the ADO.NET System.Data.DataSet.
DataAdapter s have two responsibilities: to
retrieve the results of a query and place it in a
System.Data.DataSet (when you call the
Fill( ) method), and to reconcile changes in the
System.Data.DataSet and apply changes back to the
data source (when you call the Update( ) method.
An ADO.NET provider includes its own custom
DataAdapter (such as
System.Data.SqlClient.SqlDataAdapter).
Unfortunately, DataAdapter classes have a complex
inheritance hierarchy. The base functionality is defined by two
interfaces: System.Data.IDataAdapter (which
defines the Update( ) and Fill( ) methods) and, for relational database providers, a
System.Data.IDbDataAdapter (which defines the
command properties used for interacting with the data source). The
relational database provider-specific DataAdapter
implements only one of these interfaces directly
(System.Data.IDbDataAdapter). It implements the
other indirectly by deriving from DbDataAdapter,
which in turn derives from this class. This situation is illustrated
more clearly in Figure 36-2. This allows some basic
DataAdapter functionality to be implemented in
this class (so the provider-specific DataAdapter
doesn’t need to). It also allows the
provider-specific class to use strongly typed
Command properties but still support generic
access to these properties as
System.Data.IDbCommand ...
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