pp. 490-522

1
ASP.NET Shopping Cart ServiceLecture 2

• Chapter 13
• pp. 490-522
• Profile object as persistent store for cart
• Shopping cart control
• The checkout process

2
Q. Where shall we store the cart?A. The Profile
object

• The shopping cart objects need to be in a
  persistent store. They need to continue to exist
  as the user moves from page to page.
• Recall (for the 1000th time-) that HTML is
  stateless. Thus our choices are
• A cookie
• Database records
• Session variables (why not application variables?)

3
Where to store the cart, continued

• Cookies may not be permitted on the client
  machine
• Database access can slow processing
• The winner a system maintained persistent
  object called the Profile
• An addition to the Profiles original function of
  storing login information
• Profiles are explained in Chapter 11, pp. 408-417
  and pp. 424-425

4
Profile addenda DEMO

• USB/Chapter 13/end/Web.config view profile and
  anonymous ID enabled
• USB/Chapter 11/end/Global.asax view code to
  allow anonymous shopping with transfer on actual
  login the Profile_OnMigrateAnonymous() function
• USB/Chapter 13/end/ view profile fields in
  ASPNETDB.MDF with database explorer

5
Shopping function overview
Click return to shopping
Click on item
Catalog Page
Item Page
Click Add to cart
Cart Page
Edit cart
Cart Cart Item
Then transfers to page that displays the cart
Click event code adds cart item to cart
Click checkout
Checkout Page
6
Creating the Shopping Cart Control

• Since there is no industry standard shopping
  cart protocol, Microsoft does not supply a
  pre-programmed cart control.
• You will build a shopping cart control and then
  add it to a page
• Since you are literally building the control, you
  must add the code for EVERY function you want it
  to perform!

7
Shopping cart control creation

• Begin by right-clicking on the application name
  in the Solution Explorer and thenAdd New ? Web
  User Control
• The new control behaves like a web page and has
  both a Source and a Design views. Open it in
  Design View and drag a GridView control to it.
• Note the designers of the textbook chose a
  GridView control for the display of the shopping
  cart. This was a design choice you are free to
  make different display choices, for example,
  DetailsView or a totally custom look with
  FormView.

8
Shopping cart control creation (2)

• Add GridView fields for ProductName, Quantity,
  Price, LineTotal (extension), control fields and
  a thumbnail image. The fields must have the same
  names as in the CartItem object since you are
  going to bind the DataGrid to the ShoppingCart
  object
• Now YOU must supply code for the GridView events
• Update (edit) a row (only quantity is editable)
• Cancel an edit
• Delete a row (if quantity is 0)
• Display a message if the cart is empty
• Bind the DataGrid to ShoppingCart item data
• This code must read, write and edit the
  ShoppingCart object stored in the session Profile

9
Shopping cart control creation (3)

• To make the control active it must be added to a
  web page (a standard .aspx page)
• Create a new page and drag the control (the
  .ascx) from the solution explorer onto the new
  page
• Add VB code for the events see pp. 497-499

10
Shopping cart control creation

• DEMO
• USB/Chapter 13/End/WroxUnited/ShopptingCartPage.as
  px
• Edit the GridView events the lightning bolt
  in the properties. This is where VB code is added
  for add, change, delete.
• Note that the code updates the Profile-based
  ShoppingCart and Item objects designed last week
• .NET automatically writes the Profile to the
  disk-based database ASPNETDB.MDF. This is a
  definite savings of effort the Item object
  takes much less code to update than a database.
  Remember this trick it has multiple uses.

11
Calling the shopping cart page and ADDing an item
to the cart

• We now have a nice shopping cart display but no
  way to get to it! And no way to add items!
• Both problems have the same easy solution
• Add a button to the Item display page that
• Has onclick code to add the item to the cart
• Transfers control to the shopping cart display

12
Calling the shopping cart page and ADDing an item
to the cart (2)

• DEMO
• USB/WroxUnited/WroxShopItem.aspx
• Note
• Code to pull data from controls
• Code to add item to ShoppingCart object
• Code to transfer control to the WroxShop page

13
Checking out (pp. 505-523)

• When the user has finished shopping the checkout
  process begins
• The checkout activity is a complex subprocess
• (force) Login (if not already logged in)
• Capture delivery address
• Capture payment information
• Final confirmation
• Post order (to database) and thank customer

14
Checkout Logic a brief digression

• Automating a complex series of steps, each of
  which performs multiple functions and requires
  code to be executed at a specific time is called
  PROCEDURAL PROGRAMMING
• COBOL, C, Java and JavaScript are all
  procedural languages you must handle EVERYTHING
  including ALL program flow
• In contrast, VB is an event-driven language. It
  handles most of the control logic and the
  programmer only inserts code fragments to be
  executed in response to events

15
Checkout Logic a brief digression (2)

• But sometimes the sequence VB (or .NET) assumes
  is NOT correct for what you want to do.
• Checkout is just such a task a series of
  complex subtasks have to be properly sequenced
  and checked for correctness
• The halfaed (but functional) solution to this
  in .NET is the programmable Wizard

16
Checkout Logic

• The Wizard control allows one page to behave as
  if it were multiple pages, 1 for each Wizard
  step
• You add code and controls to each step in much
  the same way as you would to an individual web
  form
• The code behind file for this (checkout) page
  does is responsible for adding the shopping cart
  to the disk-based database using ADO.NET code!

17
Checkout DEMO

• Ch 13/End/Checkout.aspx
• NOTE
• The Wizard control adding steps
• The source at each step
• The progress list of steps down the side of the
  page
• The code behind file