Tài liệu Module 1: Data-Centric Applications and ADO.NET pptx

Contents
Overview 1
Lesson: Design of Data-Centric Applications 2
Lesson: ADO.NET Architecture 9
Lesson: ADO.NET and XML 19
Multimedia: ADO.NET and XML 22
Demonstration: ADO.NET and XML 23
Review 28
Lab 1.1: Data-Centric Applications and
ADO.NET 30

Module 1: Data-Centric
Applications and
ADO.NET


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Module 1: Data-Centric Applications and ADO.NET iii


Instructor Notes
This course contains code samples in two programming languages: Microsoft
®

Visual Basic
®
and Microsoft Visual C#
™

. The use of these two programming
languages will accommodate students who are currently Visual Basic
programmers and might be considering working with Visual C#, and students
who are C, Microsoft Visual C++
®
, Java, and Visual C# programmers who do
not have Visual Basic experience. The lab exercises have solutions in both
languages. Most examples are also in both programming languages, except
when the differences between the languages are minor.
Access the code examples by clicking the hyperlinks at the bottom of the
Microsoft PowerPoint
®
slides during your presentation. The examples are
displayed in Microsoft Internet Explorer. The examples for each module are
contained in a single .htm file for that module. You can navigate to different
examples within the example files. To avoid running multiple instances of
Internet Explorer, close each instance after you have finished with a code
example.
This module teaches students about the design of data-centric applications
(including connected and disconnected environments), Microsoft ADO.NET
architecture, and ADO.NET and XML.
After completing this module, students will be able to:
!
Give examples of storage options.
!
Diagram the architecture of data-centric applications.
!
Choose a connected, disconnected, or mixed environment based on
application requirements.
!

Use the System.Data namespaces in applications.
!
Diagram the ADO.NET object model.
!
Analyze typical business scenarios.
!
Describe the use of XML in ADO.NET.

To teach this module, you need the following materials:
!
Microsoft PowerPoint file 2389B_01.ppt
!
Module 1, “Data-Centric Applications and ADO.NET”
!
Lab 1, Data-Centric Applications and ADO.NET

To prepare for this module:
!
Read all of the materials for this module.
!
Complete the practices and labs.
!
Read the latest .NET Development news at
/>d=28000519

Presentation:
60 Minutes

Lab:
30 Minutes

Required materials
Preparation tasks
iv Module 1: Data-Centric Applications and ADO.NET


This module contains multimedia animations. To start an animation, click the
movie projector button on the PowerPoint slide for the multimedia. When the
multimedia window opens, click the Start button
.

This course contains code examples that are linked to text hyperlinks at the
bottom of PowerPoint slides. These examples enable you to teach from code
examples that are too long to display on a slide. All of the code examples for
this module are contained in one .htm file. Students can copy the code directly
from the browser or from the source, and paste it into a development
environment
To display a code sample, click a text hyperlink on a slide. Each link opens an
instance of Internet Explorer and displays the code associated with the link. At
the end of each example is a link that displays a table of contents of all
examples in this module. After you have finished teaching the code for an
example, close the instance of the browser to conserve resources.
If time constraints occur, one or more practices in this module can be presented
as instructor-led demonstrations.
Multimedia
Hyperlinked code
examples
Practices
Module 1: Data-Centric Applications and ADO.NET v

How to Teach This Module
This section contains information that will help you to teach this module.
Lesson: Design of Data-Centric Applications
This section describes the instructional methods for teaching each topic in this
lesson. This lesson should not take more than 25 minutes.
Technical Notes:
!
Emphasize that ADO.NET can support any data storage format for which
there is a .NET data provider, OLE DB provider, or ODBC driver.
!
Third party organizations are likely to quickly support the .NET data
provider standard and supply native .NET data providers.

Discussion Questions: Personalize the following question to the background of
the students in your class.
• Which data storage models do you need to access in your company?

Technical Notes: The key word is constantly connected.

Be careful not to get drawn into a philosophical discussion about
what is a connected or disconnected environment.

Discussion Questions: Personalize the following questions to the background
of the students in your class.
!
What are the advantages of the connected environment?
!
What are the disadvantages of using a connected environment?

Technical Notes:

!
The key word is constantly connected.
!
Emphasize that most real-world environments use a combination of
connected and disconnected solutions.

Discussion Questions: Personalize the following question to the background of
the students in your class.
• Do your applications use a connected or disconnected environment?

Data Storage
What Is a Connected
Environment?
Warnin
g

What Is a Disconnected
Environment?
vi Module 1: Data-Centric Applications and ADO.NET


Technical Notes:
!
Emphasize that most real-world environments use a combination of
different tiered solutions.
!
Balance is a good key word here. Improving one aspect of a solution tends
to worsen another. Difficult design decisions must be made based on what is
best for a particular situation.
!

Remember KISS: “Keep It Simple, Simon”

Discussion Questions: Personalize the following questions to the background
of the students in your class.
!
What are some problems with 2-tier applications? How scalable is this type
of application?
!
What kinds of security are available with the different application models?

Transition to Practice Exercise: Instruct students to turn to the practice
exercise at the end of this topic in the student workbook.
The purpose of this practice is to relate the topics we have discussed to
applications that you have built or will build in your work environment.
Data Access
Application Models
Module 1: Data-Centric Applications and ADO.NET vii


Lesson: ADO.NET Architecture
This section describes the instructional methods for teaching each topic in this
lesson. This lesson should not take more than 20 minutes.
Technical Notes: In some ways you can think of ADO.NET as a marketing
term that covers the classes in the System.Data namespace.
Technical Notes: The students should already know how to reference
assemblies and import namespaces, but some will not, so be prepared to explain
the fundamentals of namespaces. Appendix D, “Microsoft .NET Framework
Overview,” in Course 2389B, Programming with Microsoft ADO.NET, covers
the fundamentals of Microsoft .NET, including namespaces.
Transition to Practice Exercise: Instruct students to turn to the practice

exercise at the end of this topic in the student workbook.
The purpose of this practice is to provide experience referencing an assembly
and importing a namespace.
Technical Notes:
The slide does not show all ADO classes (for example, Record and Stream).
Many students will not have used the ADO Recordset in a disconnected
scenario.
You might want to spend a few minutes explaining ADO.NET functionality and
limitations while discussing the benefits for DataSets.

Transition to Practice Exercise: Instruct students to turn to the practice
exercise at the end of this topic in the student workbook.
The purpose of this practice is to discuss different ways of using ADO.NET and
relate the classroom discussions to applications you may be building or working
with.
Technical Notes: The ADO.NET object model consists of two major parts: the
DataSet classes and the .NET data provider classes.
The DataSet class has a Tables property, which gets a collection of DataTable
objects in the DataSet, and a Relations property, which gets a collection of the
DataRelation objects in the DataSet.
What Is ADO.NET?
What Are the Data-
Related Namespaces?
Evolution of ADO to
ADO.NET
The ADO.NET Object
Model
viii Module 1: Data-Centric Applications and ADO.NET

Technical Notes: Stress to the students that the connection is open during the
processing of the DataReader, and therefore resources are being used on the
server.
Discussion Questions: Personalize the following questions to the background
of the students in your class.
Why is using the SQL Server .NET Data Provider more efficient than using the
OLE DB .NET Data Provider for SQL Server?
What is the purpose of the XxxDataReader class?
Technical Notes: Stress to the students that the connection is open during the
retrieval of the dataset, but not during the processing of the data. The
processing can include reading the rows, sorting, filtering, and editing the data.
Therefore, resources are not used on the server while this processing occurs.
Later, a new connection is made and the changes are sent to the data source.
Discussion Questions: Personalize the following question to the background of
the students in your class.
What class is used in the disconnected environment that is not used in the
connected environment?
Using ADO.NET Classes
in a Connected Scenario
Using ADO.NET Classes
in a Disconnected
Scenario
Module 1: Data-Centric Applications and ADO.NET ix


Lesson: ADO.NET and XML
This section describes the instructional methods for teaching each topic in this
lesson. This lesson should not take more than 15 minutes. ADO.NET and XML
is discussed in detail in Module 5: “Reading and Writing XML with
ADO.NET,” in Course 2389B, Programming with Microsoft ADO.NET.

Technical Notes: Do not spend long on this topic, because you will need plenty
of time for the multimedia and demonstration. Explain that ADO.NET uses
XML extensively, and that the course covers XML features in detail later.
This multimedia animation describes how a developer can use ADO.NET to
create a distributed solution to a business problem. The Visual Studio .NET
solution includes two projects. The first is an XML Web service and the second
is a Microsoft Windows
®
application that uses the Web service.
Technical Notes:
!
It is important to ensure that this demonstration goes well. Check that the
demonstration executes correctly before the course begins.
!
Familiarize yourself thoroughly with this demonstration.

ADO.NET and XML
Multimedia: ADO.NET
and XML
Demonstration:
ADO.NET and XML
x Module 1: Data-Centric Applications and ADO.NET


Review: Data-Centric Applications and ADO.NET
This section provides the answers to review questions at the end of this module.
1. What are the characteristics of a connected architecture? Describe some
scenarios where a connected architecture is appropriate.
A connected architecture is one where an application connects directly
to a data source, to query and modify the stored data.

A connected architecture is appropriate for in-house applications that
access a data source over a local area network. Another example is an
ASP.NET Web application that queries a database to generate a read-
only report of the data.


2. What are the characteristics of a disconnected architecture? Describe a
scenario where a disconnected architecture is appropriate.
A disconnected architecture is one where an application does not
connect directly to a data source. ADO.NET provides extensive support
for building disconnected applications, to meet the needs of modern-day
distributed systems.
A disconnected architecture is appropriate for mobile workers. At the
start of the day, a private copy of customer and product data can be
downloaded from the database. During the day, the worker uses and
modifies this copy of the data. At the end of the day, the worker posts
the data changes back to the database. XML Web services have an
important role to play in this style of application.


3. What are the features and advantages of the XML Web service architecture?
Business services are made available to disconnected users. XML Web
services can retrieve private copies of data from a data source to enable
users to work with the data remotely. XML Web services also allow the
user to post data updates back to the data source when required.


Module 1: Data-Centric Applications and ADO.NET xi

4. How does ADO.NET increase the interoperability and scalability of
disconnected systems?
XML makes interoperability possible. Data from a data source can be
expressed in XML format, which makes it easier to exchange the data
between application tiers and across organizational boundaries. XML is
tightly integrated into the design and philosophy of ADO.NET.
Scalability is achieved by enabling data to be cached locally in in-
memory caches. This reduces the number of active connections and
database locks that are required, which means that more users can be
supported at the same time.


5. What is a DataSet, and why is it important in ADO.NET?
The DataSet class is the most fundamental concept in the design of the
ADO.NET disconnected architecture. A DataSet is an in-memory cache
of data tables, relationships, and constraints. You can populate a
DataSet from a SQL query, an XML document, or by creating tables,
relations, and constraints programmatically by using code.
DataSets usually contain a subset of the data in a central database.
You can manipulate a DataSet in a disconnected application. You can
also write out the contents of a DataSet in XML format, and pass it to
other applications and services.


6. Which .NET data providers are included in the .NET Framework?
The .NET Framework includes two data providers: the SQL Server
.NET Data Provider, and the OLE DB .NET Data Provider.
The SQL Server .NET Data Provider gives optimized access to
SQL Server 2000 and SQL Server 7.0 databases.
The OLE DB .NET Data Provider gives access to SQL Server 6.5 (and

earlier), Oracle, Sybase, and other databases.




Module 1: Data-Centric Applications and ADO.NET 1


Overview
!
Design of Data-Centric Applications
!
ADO.NET Architecture
!
ADO.NET and XML

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This module describes the design of data-centric applications, the Microsoft
®

ADO.NET architecture, and the integration between ADO.NET and XML.
After completing this module, you will be able to:
!
Give examples of storage options.
!
Diagram the architecture of data-centric applications.

!
Choose a connected, disconnected, or mixed environment based on
application requirements.
!
Use the System.Data namespaces in applications.
!
Diagram the ADO.NET object model.
!
Analyze typical business scenarios.
!
Explain how to use ADO.NET with XML.

Introduction
Objectives
2 Module 1: Data-Centric Applications and ADO.NET


Lesson: Design of Data-Centric Applications
!
Data Storage
!
What Is a Connected Environment?
!
What Is a Disconnected Environment?
!
Data Access Application Models

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This lesson describes the design of data-centric application architecture and
data storage options.
After completing this lesson, you will be able to:
!
Give examples of common types of data storage.
!
Choose between a connected and disconnected application environment.
!
Diagram how data access application models have evolved.

Introduction
Lesson ob
j
ectives
Module 1: Data-Centric Applications and ADO.NET 3


Data Storage
ADO.NET supports the following types of data storage:
!
Unstructured
!
Structured, non-hierarchical data
" Comma Separated Value (CSV) files, Microsoft Excel
spreadsheets, Microsoft Exchange files, Active
Directory files, and others
!
Hierarchical

" XML documents and others
!
Relational database
" SQL Server, Oracle, Access, and others

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Data storage is a method of storing specific items that together constitute a unit
of information. Individual data items themselves are of little use; they become
value resources only when put into context with other data items.
The following table describes different methods of data storage.
Type Characteristics Examples

Unstructured Data has no logical order. Simple memos
Structured, non-
hierarchical
Data is separated into units, but the
units are organized strictly by their
order.
Comma Separated Value
(CSV) files or tab-
separated files, Microsoft
Excel spreadsheets,
Microsoft Exchange files,
Microsoft Active
Directory
™

files, indexed
sequential access method
(ISAM) files
Hierarchical Data is organized in a tree
structure, with nodes that contain
other nodes.
XML data documents
Relational
database
Data is organized in tables, with
columns containing a specific type
of data and rows containing a
single record. Tables can be related
over columns with identical data.
Microsoft SQL Server
™

and Microsoft Access
databases, Oracle databases

Object-oriented
database
Data is organized as objects. Objectivity/DB

ADO.NET can support all of the data formats in the preceding table.
Definition of data
stora
g
e
T

y
pes of data stora
g
e
ADO.NET support
4 Module 1: Data-Centric Applications and ADO.NET


What Is a Connected Environment?
!
A connected environment is one in which users are
constantly connected to a data source
!
Advantages:
" Environment is easier to secure
" Concurrency is more easily controlled
" Data is more likely to be current than in other scenarios
!
Disadvantages:
" Must have a constant network connection
" Scalability

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For much of the history of computers, the only environment available was the
connected environment.
A connected environment is one in which a user or an application is constantly

connected to a data source.
A connected scenario offers the following advantages:
!
A secure environment is easier to maintain.
!
Concurrency is easier to control.
!
Data is more likely to be current than in other scenarios.

A connected scenario has the following disadvantages:
!
It must have a constant network connection.
!
Scalability

The following are examples of connected environments:
!
A factory that requires a real-time connection to monitor production output
and storage
!
A brokerage house that requires a constant connection to stock quotes

Introduction
Definition
Advantages
Disadvantages
Examples
Module 1: Data-Centric Applications and ADO.NET 5

What Is a Disconnected Environment?
!
In a disconnected environment, a subset of data from a central
data store can be copied and modified independently, and the
changes merged back into the central data store
!
Advantages
"
You can work at any time that is convenient for you, and can
connect to a data source at any time to process requests
"
Other users can use the connection
"
A disconnected environment improves the scalability and
performance of applications
!
Disadvantages
"
Data is not always up to date
"
Change conflicts can occur and must be resolved

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With the advent of the Internet, disconnected work scenarios have become
commonplace, and with the increasing use of handheld devices, disconnected
scenarios are becoming nearly universal. Laptop, notebook, and other portable

computers allow you to use applications when you are disconnected from
servers or databases.
In many situations, people do not work entirely in a connected or disconnected
environment, but rather in an environment that combines the two approaches.
A disconnected environment is one in which a user or an application is not
constantly connected to a source of data. Mobile users who work with laptop
computers are the primary users in disconnected environments. Users can take a
subset of data with them on a disconnected computer, and then merge changes
back into the central data store.
A disconnected environment provides the following advantages:
!
You can work at any time that is convenient for you, and can connect to a
data source at any time to process requests.
!
Other users can use the connection.
!
A disconnected environment improves the scalability and performance of
applications.

A disconnected environment has the following disadvantages:
!
Data is not always up to date.
!
Change conflicts can occur and must be resolved.

A farmer has a Microsoft Windows
®
CE device running SQL Server CE that he
uses to keep track of livestock when animals are born.
Introduction

Definition
Advantages
Disadvantages
Example
6 Module 1: Data-Centric Applications and ADO.NET


Data Access Application Models
Evolution of data access
1-Tier
(monolithic)
Client logic
Business logic
Data storage
3-Tier
“Thin” Client
N-Tier
2-Tier
“Fat” Client
Internet
XML Web
service
XML Web
service

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Data access models have evolved with the evolution of computers, from highly
localized to highly distributed. As the number of users and the amount of data
increased, data access models evolved from a single user on a single application
to multiple users on the Internet. The latest development in this evolution is the
XML Web service model.
Within a data access model, a tier is a logical level or layer at which the logical
components of an application reside, not a physical tier. Tiers can reside on one
or more computers, or physical tiers. The number of tiers refers to the number
of levels, not the number of physical computers, into which services are
divided. These levels typically include the following:
!
Client tier, also known as the presentation or user services layer. This tier
contains the user interface.
!
Business logic tier, which contains the logic that interacts with the source of
data. This “middle” tier contains the part of the application that interacts
with the data; for example, creating a connection to the source of the data.
The business logic tier is often physically implemented in all tiers; for
example, as stored procedures in the data store, as classes within an
application server, or as code within the client application.
!
Data services tier, which contains the data that the business logic uses in the
applications.
!
Interoperability tier, which contains the logic that allows interaction
between applications on different operating systems, or different types of
data. For example, XML Web services can be hosted on any operating
system.

Introduction

Definition of tier
Module 1: Data-Centric Applications and ADO.NET 7


The major advantage of adding tiers is the ability to scale applications. Each
additional tier allows you to add more users and isolate a level of application
logic. Isolating the logic enables you to make changes to a specific area of an
application without requiring changes to the other tiers.
For example, in a 1-tier application, a change to any level of logic requires that
the entire application be recompiled and redistributed.
The following table compares the different types of data access models.

Model Description Advantages Disadvantages

1-tier, or Monolithic This model typically involves
a single user and all three
layers in a single computer.
For example, an old-style
Microsoft Access database
with a single user.
Because everything is in
one place, all components
are easily accessible.
Program update requires
source code to be
modified, recompiled, and
redistributed for every
user. This model provides
no real ability to scale.
2-tier – client/server The user layer and business

logic layer reside in one tier,
data services on another. This
model typically involves two
or more computers. For
example, a business
p
ersonnel database. Often the
business logic is split
between the two tiers: some
logic in the client application,
and some as stored
procedures in the data tier.
Provides some separation
of functions.
Difficult to scale because
the client is a “fat client”
that contains both the
presentation and business
logic layers.
Software distribution and
maintenance problems.
3-tier Each service is in a separate
layer. Business logic moves
into a new “Middle tier.”
Good separation of
functions. The client layer
is a “thin client” that
contains only the client
logic, or presentation
layer.

More complex to manage.
Security is not as
scalable/flexible as n-tier.

N-tier An enterprise-level personnel
database where several
clients access a single
application server. New tiers
can be added as new logical
needs occur.
Allows different
applications on different
operating systems to
interact with both the user
and the data.

Security issues.
Remote procedure calls
(RPC) cannot pass
through firewalls.
N-tier with Web interface

Services are distributed
between the Internet and
intranet, with additional tier
and additional servers
dedicated to the network.
Zero client deployment
costs. The only updates are
to Web/application

servers.
HTTP can go through
firewalls.
Security issues.

Benefits of tiers
Evolution of access
models
8 Module 1: Data-Centric Applications and ADO.NET


As a general guideline, keep in mind that as the number of tiers increases, the
scalability and complexity of the data access model increase.

Group discussion. Ask a student to come to the front of the class, think of a
database application that he or she has developed in the past, and then use the
whiteboard to:
1. Draw a diagram showing the data access application model the database
application used.
2. Draw the data storage formats the student needed to access.

Did the architecture use a connected or disconnected environment?
Balance
Practice
N
umber of tiers
Complexity, scalability
Module 1: Data-Centric Applications and ADO.NET 9

Lesson: ADO.NET Architecture
!
What Is ADO.NET?
!
What Are the Data-Related Namespaces?
!
Evolution of ADO to ADO.NET
!
The ADO.NET Object Model
!
Using ADO.NET Classes in a Connected Scenario
!
Using ADO.NET Classes in a Disconnected Scenario

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This lesson introduces ADO.NET and establishes its place in the Microsoft
.NET Framework.
After completing this lesson, you will be able to:
!
Explain how to use ADO.NET.
!
Discuss how ADO.NET is divided into namespaces.
!
Diagram the ADO.NET object model.

Introduction

Lesson ob
j
ectives
10 Module 1: Data-Centric Applications and ADO.NET


What Is ADO.NET?
ADO.NET is a set of classes for working with data.
It provides:
!
An evolutionary, more flexible successor to ADO
!
A system designed for disconnected environments
!
A programming model with advanced XML support
!
A set of classes, interfaces, structures, and
enumerations that manage data access from within
the .NET Framework

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ADO.NET is the next step in the evolution of Microsoft ActiveX
®
Data Objects
(ADO). It does not share the same programming model, but shares much of the
ADO functionality.

ADO.NET is a set of classes for working with data.
As application development has evolved, new applications have become loosely
coupled based on the Web application model. An increasing number of
applications use XML to encode data to be passed over network connections.
ADO.NET provides a programming model that incorporates features of both
XML and ADO.NET within the .NET Framework.
ADO.NET provides the following advantages over other data access models
and components:
!
Interoperability. ADO.NET uses XML as the format for transmitting data
from a data source to a local in-memory copy of the data.
!
Maintainability. When an increasing number of users work with an
application, the increased use can strain resources. By using n-tier
applications, you can spread application logic across additional tiers.
ADO.NET architecture uses local in-memory caches to hold copies of data,
making it easy for additional tiers to trade information.
!
Programmability. The ADO.NET programming model uses strongly typed
data. Strongly typed data makes code more concise and easier to write
because Microsoft Visual Studio
®
.NET provides statement completion.
!
Performance. ADO.NET helps you to avoid costly data type conversions
because of its use of strongly typed data.
!
Scalability. The ADO.NET programming model encourages programmers
to conserve system resources for applications that run over the Web.
Because data is held locally in in-memory caches, there is no need to retain

database locks or maintain active database connections for extended
periods.
Introduction
Definition
Business use case
Benefits
Module 1: Data-Centric Applications and ADO.NET 11


What Are the Data-Related Namespaces?
!
The data-related namespaces include:
" System.Data
" System.Data.Common
" System.Data.SqlClient
" System.Data.OleDb
" System.Data.SqlTypes
" System.Xml
!
Practice

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The .NET Framework divides functionality into logical namespaces, and
ADO.NET is no exception. ADO.NET is implemented primarily in the
System.Data namespace hierarchy, which physically resides in the
System.Data.dll assembly. Some parts of ADO.NET are part of the System.Xml

namespace hierarchy, for example the XmlDataDocument class.
The following table describes the data-related namespaces.
Namespace Description

System.Data Core of ADO.NET. Includes classes that make up the
disconnected part of the ADO.NET architecture. For
example, the DataSet classes.
System.Data.Common Utility classes and interfaces that are inherited and
implemented by .NET data providers.
System.Data.SqlClient SQL Server .NET Data Provider.
System.Data.OleDb OLE DB .NET Data Provider.
System.Data.SqlTypes Classes and structures for native SQL Server data
types. A safer, faster alternative to other data types.
System.Xml Classes, interfaces, and enumerations that provide
standards-based support for processing XML. For
example, the XmlDataDocument class.

Introduction
The data-related
namespaces
12 Module 1: Data-Centric Applications and ADO.NET


!
Reference the System.Data assembly, import the System.Data
namespace, and declare an object variable
1. Start the Visual Studio .NET development environment.
2. On the File menu, point to New, and then click Project.
3. In the New Project dialog box, select the following options, and then click
OK.

Option Selection

Project Types Visual Basic Projects (or Visual C# Projects if you prefer)
Templates Windows Application
Name MyWindowsApplication
Location <install folder>\Practices\Mod01

4. In the Solution Explorer, right-click the References folder and choose Add
Reference.
5. Select the System.Data.dll assembly, click Select, and then click OK.

Referencing the System.Data assembly is done by default in Windows
Application projects, so the previous two steps are not usually necessary.

6. Open the code editor, and insert the following code before the existing code:
' Visual Basic
Imports System.Data
Imports System.Data.SqlClient

// Visual C#
using System.Data.SqlClient;


Visual C# includes a using System.Data; statement by default in
Windows Application projects (as well as a few other using statements), which
is why that line is missing in the code above. If you add the preceding code to
all subsequent classes, you will be able to declare object variables without
having to explicitly specify the namespace.

7. Insert the following code in the Form1_Load event. Notice that you do not

need to specify the namespace for the DataSet and SqlConnection classes:
' Visual Basic
Dim dsNorthwind As DataSet
Dim cnNorthwind As SqlConnection

// Visual C#
DataSet dsNorthwind;
SqlConnection cnNorthwind;

8. Save the changes to your project and close the Visual Studio .NET
development environment.

Practice
Note
Note
Module 1: Data-Centric Applications and ADO.NET 13


Evolution of ADO to ADO.NET
Connection
Connection
ADO
ADO.NET
Command
Command
Recordset
Recordset
XxxConnection
XxxConnection
XxxCommand

XxxCommand
DataSet
DataSet
XxxTransaction
XxxTransaction
XxxDataReader
XxxDataReader
XxxDataAdapter
XxxDataAdapter

*****************************
ILLEGAL FOR NON
-
TRAINER USE
******************************
Many changes have been made between ADO and ADO.NET. Most of these
changes are a response to studies of how developers use (and misuse) ADO.
Other changes have made ADO.NET more flexible, more powerful, and more
scalable than ADO.
Because not all .NET data providers provide transactional functionality,
ADO.NET moves that functionality into a separate class. This also means that
the new ADO.NET connection object is more lightweight than the previous
ADO connection object.
The ADO Recordset was a huge object in ADO. It provided the ability to
support multiple types of cursors, from a fast, lightweight “firehose” cursor, to
a disconnected client-side cursor that supported change tracking, optimistic
locking, and automatic batch updates of a central database. However, all of this
functionality was difficult (or impossible) to customize.
ADO.NET breaks the functionality of the old ADO Recordset into multiple
classes, thereby allowing a focused approach to developing code. The Data

Reader is the equivalent of a “firehose” cursor. The DataSet is a disconnected
data cache with tracking and control binding functionality. The DataAdapter
provides the ability to completely customize how the central data store is
updated with the changes to a DataSet.
See Appendix B, “ADO and ADO.NET Comparison,” for more information
about the reasons for the changes between ADO and ADO.NET.
Introduction
Divide and conquer
Reference