ASP.NET 2.0 Everyday Apps For Dumies 2006 phần 5 pot

data into another table that also has an identity column. In that case, the

@@IDENTITY function returns the identity value for the second table. Fortu￾nately, the Cart database doesn’t use triggers, so the @@IDENTITY function

will correctly return the identity value generated by the Orders table.

Connecting to the database

The connection string used to access the Cart database is stored in the

application’s web.config file, like this:

<connectionStrings>

<add name=”ConnectionString”

connectionString=”Data

Source=localhost\SQLExpress;

Initial Catalog=Cart;Integrated Security=True”/>

</connectionStrings>

The only place in the application that references this connection string is

here in the web.config file. This makes it easy to relocate the database

when you put the application into production.

The Application’s Folders

The Shopping Cart application includes the following folders:

(Root): The application’s root folder contains the application’s six pages

(Default.aspx, Product.aspx, Cart.aspx, CheckOut.aspx, and

Completed.aspx) as well as the Master Page (Default.master).

App_Data: This folder is designed to store databases used by the applica￾tion. However, this particular application uses a database that’s stored

in a location that’s determined by SQL Server. So the database for our

Cart isn’t actually stored in this folder. (If you use the script presented in

Listing 6-1 to create the database, the database file is stored in C:\Apps.)

App_Code: This folder contains the C# or Visual Basic code files that

define the classes used by the application. For more information about

these classes, see the section “Designing the Classes” later in this chapter.

Images: Here, you’ll find the banner image displayed by the Master Page

and the image files that show pictures of the store’s products.

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Designing the Classes

Unlike most of the other applications presented in this book, the Shopping

Cart application depends on several classes that both define the business

objects used by the program as well as provide the database access. In par￾ticular, the application uses the following classes:

Customer: Represents a single customer.

ShoppingCart: Represents the user’s shopping cart.

CartItem: Represents an item in the user’s shopping cart.

Order: Represents an order.

OrderDB: Handles the details of writing an order to the database.

The following sections describe each of these classes in detail.

The Customer class

The Customer class represents a single customer. Its constructors and prop￾erties are spelled out in Table 6-4.

Table 6-4 The Customer Class

Constructor Description

Customer() Creates an instance of the Customer

class with default property values.

Customer(string lastName, Creates an instance of the Customer

string firstName, string class with the specified property values.

address, string city,

string state, string

zipCode, string

phoneNumber, string email)

Property Description

string LastName The customer’s last name.

string FirstName The customer’s first name.

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Property Description

string Address The customer’s street address.

string City The customer’s city.

string State The customer’s state.

string zipCode The customer’s Zip code.

string phoneNumber The customer’s phone number.

string email The customer’s e-mail address.

The ShoppingCart class

The ShoppingCart class represents a user’s shopping cart. Its constructors,

properties, and methods are listed in Table 6-5.

Table 6-5 The ShoppingCart class

Constructor Description

ShoppingCart() Creates a new shopping cart with no

items.

Property Description

int Count The number of items in the shopping cart.

Method Description

List<CartItem> GetItems() Returns a List object that contains one

CartItem object for each item in the

shopping cart.

void AddItem(string id, Adds a new item with the specified

string name, decimal price) product ID, name, and price.

void UpdateQuantity Updates the quantity at the specified

(int index, int quantity) index.

void DeleteItem(int index) Deletes the item at the specified index.

string PhoneNumber The customer’s phone number.

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