Chương 3 Windows Database Applications

Chapter Windows Database Applications 2 Universal Data Access UDA Microsoft’s strategy for accessing data for multiple providers Goal is to access any type of data from any applicatio

Chapter

Windows Database

Applications

2

Universal Data Access (UDA)

Microsoft’s strategy for accessing data for multiple providers

Goal is to access any type of data from any application on any type of computer

OLEDB

Technology designed to implement the UDA concept

Standardized interface that allows reference to data from any source using the same

programming tools

From DAO To ADO.NET

Data Access Objects (DAO 1-tier ) enabled programmers to access local databases in the Microsoft Jet Database Engine format, which were primarily Indexed Sequential Access Method (ISAM) files

After DAO came RDO Remote Data Objects (2-tier)

After RDO came ADO ActiveX Data Objects (ADO 1 to n-tier)) These data access technologies were designed for a client / server paradigm However the tendency of distributed computing forced the development

of a new technology to solve the problems of data manipulation on a n-tier architecture ADO.NET is the evolution of ADO and its components have benn designed to function properly on a n-tier architecture

5

ADO.NET

ActiveX Data Objects    ADO

ActiveX Data Objects    ADO

ADO.NET latest database object model

Allows CSharp programmers to use a standard set

of objects to refer to data from any source

.NET approach uses disconnected datasets with

common data representation (data types) from

multiple sources

6

ADO.NET Components

Data Providers – manipulate the data using SQL statements

or stored procedures

SQLClient  for SQL Server

OleDbClient  for all other database formats

An ODBC provider is available for download

Data Provider Objects

Connection object (OleDbConnection)– link to a data source

DataAdapter object(OleDbDataAdapter) – handles retrieving and updating data in a DataSet object

Command object (OleDbCommand) – storeprocedure and executes SQL statements

DataReader object (OleDbDataReader) –

for read-only access

8

ADO.NET Components

DataSet Objects  holds a copy of the data in

memory

Dataset objects can be populated with data from many sources

Regardless of the data source, code handles DataSet objects the same

Dataset objects hold one or more DataTable objects

CÀI ðẶT MSDN (Help)

Mô Hình Kết Nối

Data Adapter

DataSet

Web

Form WindowsForm

Windows Form

Data Adapter DataSet

Windows Form

DataSet DataView

Windows Form

Data Reader

NET Data Provider Objects

SelectCommand

InsertCommand

UpdateCommand

DeleteCommand

Connection

.NET Data Provider

Command

Data Adapter

DataReader

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The DataSet Object Model

DataSet

DataTable Collection

DataTable

DataRowCollection

DataColumnCollection

ParentRelations

ChildRelations

ConstraintCollection

DataView

DataRelationCollection

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The DataSet Object Model

DataTable Characteristics

A primary key field (or combination of fields) uniquely identifies each record

A relational database contains multiple tables

Relationships between tables are established using

a foreign key

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Multitier Applications

Data Retrieval Data storage Business Object

Validation Calculations Business logic Business rules

User Interface

Forms

Controls

Menus

Data Tier Business Tier

Presentation Tier

Multitier Applications

Presentation tier  the user interface

Business tier  class(es) that handle the data

Calculations

Validation to enforce business rules

Data tier  retrieving and storing the data in a

Display the DataSet in the DataGrid

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Display the DataSet in the DataGrid

18

Display the DataSet in the DataGrid

Display the DataSet in the DataGrid

Connection

Data Adapter

Data

Source

DataSet

Web

Form WindowsForm

Presentation Tier

Data Tier