Page 104 - DCAP312_WEB_TECHNOLOGIES_II

Web Technologies-II

Notes Figure 5.2: DataSet Architecture

DATASET

Data Table Collections
Data Table
Data Row Collection

Data D Coloumn Collection
Constraint Collection

Data Relation Collection

The Dataset contains the copy of the data we requested. The Dataset contains more than one
Table at a time. We can set up Data Relations between these tables within the DataSet. The
data set may comprise data for one or more members, corresponding to the number of rows.
The DataAdapter object allows us to populate DataTables in a DataSet. We can use Fill method
of the DataAdapter for populating data in a Dataset. The DataSet can be filled either from a
data source or dynamically. A DataSet can be saved to an XML file and then loaded back into
memory very easily.

5.6 ADO.NET DataReader

DataReader Object in ADO.NET is a stream-based, forward-only, read-only retrieval of query
output from the Data Sources, which do not update the data. The DataReader cannot be shaped
directly from code; they can make only by calling the ExecuteReader process of a Command
Object.

Figure 5.3: DataReader Hierarchy

Data Reader
Command

Connection

Data Source

SqlDataReader sqlReader = sqlCmd.ExecuteReader();

The DataReader Object provides an association oriented data entrée to the Data Sources.
A Connection Object can contain only one DataReader at a time and the connection in the
DataReader remains open, also it cannot be used for any other purpose while data is being
accessed. When we started to read from a DataReader it should always be open and positioned
prior to the first record. The Read() method in the DataReader is used to read the rows from
DataReader and it always moves forward to a new valid row, if any row exist.
DataReader.Read();

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