Building multitiers program doc

Building multitiers program
Building multitiers program
Week 9
Contents
1. Review OOP
2. Three-tier application
3. Implementing 3-tier
Slide 2
Create class

Add new class: menu Project->Add Class

Create properties for a class

Create methods for a class

Create events for class
Slide 3
Creating properties for a class

Declare all variables in a class as private (encapsulation)

private properties must be assigned values and can be
get values

through get/set
public dataType myProperty {
get { return propertyName; }
set { propertyName = value; }
}
Slide 4

Creating methods: Write constructors

A constructor is a special method that used to initialize the
properties of the object

A constructor is invoked when the object gets instantiated

Note to write a constructor:

The name of the constructor and the name of the class are
the same

A constructor does not return value, not even void

A class can have multiple constructors (overloaded
constructors)
public ClassName (parameterList)
{
}
Instantiating an object

To instantiate an object, using the new keyword

Example:
Lop l = new Lop();
Lop c;
c = new Lop(“NCTH2K”, “Cao dang nghe 2K”);
Slide 6
ClassName object = new ClassName (…);
ClassName object;

object = new ClassName (…);
Using properties, methods of a class

Call methods or properties of a class

Using
dot
operator

Get/set methods:

get: variable = object.propertyName

set: object.propertyName = variable

Example:
SinhVien sv = new SinhVien();
sv.HoTen = “Nguyen Van An”;
sv.DiemLT = 5;
sv.DiemTH = 10;
lblTB.Text = sv.DiemTB().ToString();
MessageBox.Show(sv.HoTen + “ có ĐTB = ” + sv.DiemTB());
Slide 7
Contents
1. Review OOP
2. Three-tier application
3. Implementing 3-tier
Slide 8
2. Three-tier application
2.1 What is a 3-tier architecture?

2.2 What is the need for dividing the code in 3-tiers?
2.3 Designing 3-tier
Slide 9
2.1 What is a 3-tier architecture?

Three-tier (layer) is a client-server
architecture in which the
user
interface
,
business rules
and
data
access
are developed and maintained
as independent modules

There are:

Tier 1: Presentation tier

Tier 2: Business Logic tier

Tier 3: Data Access tier
Slide 10
2- 11
2.2 What is the need for dividing the code in
3-tiers?

Reusability


E.g. if we have a module that handles adding, updating, deleting
and finding customers in the system, we can use it in any
other project that might involve maintaining customers

Transformation of the system is easy

E.g. if we are moving from SQL Server data storage to Oracle
there shouldn’t be any changes required in the business layer
component and in the GUI component.

Change management of the system is easy

E.g. if GST (TAX) is changed from 10% to 15% we only need
to update the business logic component
Slide 12
2.3 Designing 3-tiers:
Data Access layer

The
Data Access Logic
component provide methods for
querying and updating data (relational databases, file
system,…)

Each
Data Access Logic
component typically provides
methods for inserting, deleting, updating and retrieving
operations relating to a specific business entity in the

application

When the application contains multiple Data Access Logic
components, you may use a generic data access component
to manage database connections, execute commands,…
2.3 Designing 3-tiers:
Data Access layer
DACommon
- conn : OleDbConnection
+ getTable( sql: string ) : DataTable
+ Update( tableUpdate : DataTable , tableName : string ):
void
Slide 14
Customers
- dacommon : DACommon
+ getTable() : DataTable
+ insert (fields in database) : bool
+ delete (primary fields in database) : bool
+ update (fields in database) : bool
+ find (some fields in database) : DataTable

Products
- dacommon : DACommon
+ getTable() : DataTable
+ insert (fields in database) : bool
+ delete (primary fields in database) : bool
+ update (fields in database) : bool
+ find (some fields in database) : DataTable

2.3 Designing 3-tiers:

Business Logic layer

The
Business Logic layer
contains classes that handle the
data

Functionality

To call Data Access Logic components to retrieve and/or
update application data

Calculations

Validation to enforce business rules
2.3 Designing 3-tiers:
Presentation layer

The
Presentation

layer
contains the components that are
required to enable user interaction with the application 
User Interface

Functionality

Receive and send data to the business logic tier


Acquire data from users

Restrict the types of input a user can enter

Perform simple mapping and transformations of the
information provided by the user controls to values needed
by the underlying components
Contents
1. Review OOP
2. Three-tier application
3. Implementing three-tier

Using single Project

Using multiple Project:

Window Application

Class Library
Slide 17