Databases and Data Access

Introduction to ADO.NET ADO.NET objects ADP.NET namespaces Differences between ADO and ADO.NET

ADO.NET OverviewLooking Back

ADO (ActiveX Data Objects) Simple component-based, object-oriented interface Provides a programming model to OLE DB accessible

outside of C++

ADO.NET OverviewWhat Is ADO.NET?

ADO .NET is a collection of classes, interfaces, structures, and enumerated types that manage data access from relational data stores within the .NET Framework These collections are organized into namespaces:

System.Data, System.Data.OleDb, System.Data.SqlClient, etc.

ADO .NET is an evolution from ADO.The next generation of ADO

Managed Providers

It performs operation of communicating  with the database

Similar to ODBC driver or OLEDB provider ADO.NET currently provides two

distinct managed providers The SQL Server managed provider is used with SQL

server OLEDB managed provider is used to communicate

with any OLEDB compliant database like Access or Oracle.

Data access namespaces

System.Data System.Data.OleDb System.Data.SQLClient System.Data.SQLTypes System.Data.XML

Main objects of ADO.NET

OleDbConnection / SQLConnection OleDbCommand / SQLCommand OleDbDataReader / SQLDataReader OleDbDataAdapter / SQLDataAdapter OleDbParameter / SQLParameter DataSet DataTable DataView DataRow DataColumn

SQL Managed Provider

SQL ServerDatabase

ADO.NET OverviewManaged Providers

ADO.NET Managed Provider

ADO Managed Provider

OLE DB Provider

Database

Your Application

ADO.NET OverviewData Access Styles

Connected: Forward-only, read-only Application issues query then reads back results and

processes them “Firehose” cursor DataReader object

Disconnected Application issues query then retrieves and stores

results for processing Minimizes time connected to database DataSet object

ADO.NET objects

These objects are divided into two groups

To manage data (DataSet,DataTable,DataRow,DataRelation)

To connect data(Connections,DataReader)

What is DataSet,DataAdapter

Dataset is an in-memory disconnected

representation of data from actual database

Since dataset is totally disconnected from the

database there must be some means of

communication between the dataset and the

database

DataAdapter is used for that purpose.

Functions of DataAdapter

Populate the dataset by fetching data from database

Updating changes made to the dataset back to the database

Changes made to the dataset are not written to the database unless explicitly updated

via DataAdapter.

DataSet

The DataSet object stores the disconnected data

from a database and allows you to manipulate it

as a single object

The DataSet Objects inturn has two other

objects DataTable,DataRelation

ADO.NET Classes DataSet

DataSet

DataTable

DataRelation

DataRow

DataColumn

DataTable

It consists collection of DataRow and DataColumn

DataRow

Represents a single row of information

Individual values can be accessed using the field

names

DataColumn

Does not hold any data instead information

about the column such as Datatype,default value

DataRelation

Each DataRelation Object represents a single

parent/Child relationship between two different

datasets

DataView-Used to bind data in the DataTable

object

Displays data or it can also filter and sort data

ADO.NET Classes DataRelation

Relates two DataTables via DataColumns

DataType value of both DataColumns must

be identical

Updates can be cascaded to child DataTables

Modifications that invalidate the relation are

disallowed

The data Source Interaction

Web pageConnection objectcommandDataReader

Data Store

ADO.NET ClassesIDbConnection Interface

Creates a unique session with a data source Implemented by SqlDbConnection and OleDbConnection

Functionality Open, close connections Begin transactions

IDbTransaction provide Commit and Rollback methods

Used in conjunction with IDbCommand and IDataAdapter objects

ADO.NET Classes IDbCommand Interface

Represents a statement to be sent to a data source Usually, but not necessarily SQL

Implemented by OleDbCommand and SqlCommand

Functionality Define statement to execute Execute statement Pass and retrieve parameters Create a prepared (compiled) version of command

ExecuteReader returns rows ExecuteNonQuery doesn’t ExecuteScalar returns single value

ADO.NET Classes System.Data.OleDb Namespace

Managed provider for use with OLEDB providers SQLOLEDB (SQL Server) – use System.Data.SQL MSDAORA (Oracle) JOLT (Jet) OLEDB for ODBC providers

OleDbConnection, OleDbCommand and OleDbDataReader classes

Classes for error handling Classes for connection pooling

ADO.NET Classes DataSet

A collection of tables Has no knowledge of the source of the data Keeps track of all relationships among tables Rich programming model (has objects for tables,

columns, relationships, and so on) Remembers original and current state of data Can dynamically modify data and metadata Native serialization format is XML Located in System.Data

ADO.NET Classes System.Data.SqlClient Namespace

Managed provider native to SQL Server Built on TDS (Tabular Data Stream) for high

performance in SQL Server SqlConnection, SqlCommand and SqlDataReader classes

Classes for Error handling Connection pooling (implicitly enabled by default )

System.Data.SqlTypes provides classes for native SQL Server data types

ADO.NET Classes IDataAdapter Interface

Populates or sends updates to a DataSet Implemented by OleDbDataAdapter and SqlDataAdapter

Not connection based Represents an asynchronous approach A superset of a command object Contains four default command objects for

Select, Insert, Update, and Delete

Conclusion

Database Theory and History Relational Database Concepts and Terminology ADO.NET Overview ADO.NET Classes

AppendixADO vs. ADO.NET

ADO is a slower automation layer over OLE DB for use in Visual Basic, etc.

ADO.NET provides direct, fast access to data from any language

ADO.NET essentially has merged OLE DB and ADO into a single layer

AppendixADO vs. ADO.NET

Feature ADO ADO.NETMemory-resident Data Representation

Uses RecordSet, which can contain one table

Uses DataSet, which can contain one or more tables represented by DataTables

Relationship Between Multiple Tables

Require the JOIN query Supports the DataRelation object

Data Visitation Scans RecordSet rows sequentially

Uses a navigation paradigm for non-sequential access

Disconnected Access Provided by RecordSet but typically supports connected access

Communicates with standardized calls to the DataAdapter

AppendixADO vs. ADO.NET

Feature ADO ADO.NETProgrammability Uses Connection object to

transmit commandsUses strongly typed programming characteristics of XML

Sharing Disconnected Data Between Tiers or Components

Uses COM marshalling to transmit disconnected Recordset

Transmits a DataSet with an XML file

Transmitting Data Through Firewalls

Problematic because firewalls are typically configured to prevent system-level requests

Supported, DataSet object use XML, which can pass through firewalls

Scalability Database locks and active database connections for long durations

Disconnected access to database data without retaining database locks