Structure

1
Structure

• Main function to create records
• Declared in a module or class
• For example,

Name of the structure
Public Structure item Public id As
String Public price As Decimal End
Structure
item
Id Price
2
Public products(1) as item products is an
array with 2 records
0
1
products
id price
id price
products(0).id 101 products(0).price
19.99 products(1).id 102 products(1).price
15.05
3
Structure Declaration
Module Module1 Public Structure item
Public id As String Public price As
Decimal End Structure Public products(1)
As item End Module
4
ArrayList

• A dynamic array (size not fixed) can add and
  remove items from an arrayList, index is
  zero-based.
• To create an ArrayList
• Dim Cart as New ArrayList
• To add an object to the ArrayList
• Cart.Add(products(1))
• Cart.Add(products(0))
• What value does Cart(0).id have?

5
Add an item to Cart and dynamically generate two
labels
Cart.Add(products(0)) add first
item to Cart For I 0 to 1 generate two
labels, one in each iteration Dim Mylabel as
new label create a new label
Me.Controls.Add(mylabel) add the
label to form If I 0 then
Mylabel.left 50 Mylabel.text
cart(0).id display id of the first item
in cart else Mylabel.left 100
Mylabel.text cart(0).price display
price of the first item in cart End if Next
6
ArrayList

• To remove items
• Cart.Remove(products(0)) remove an object
• Cart.RemoveAt(1) remove the second element

Dim myItem As item For Each myItem
In cart If myItem.id 101 Then
cart.Remove(myItem)
Exit For End If Next
7
ArrayList

• Property Count
• Property Indexof returns the index of an
  element of arraylist

Index value
Button2 clicked
8
(No Transcript)
9
Create event handlers at runtime
10
Create a new button, which can be clicked
11
AddHandler Statement
General form AddHandler control.event, New
System.EventHandler(AddressOf subXYZ)
It connects control.event to subXYZ, a
pre-written procedure.
Private Sub createNewButton_Click(ByVal sender
As System.Object, ByVal e As System.EventArgs)
Handles Button1.Click Dim b As New
Button Me.Controls.Add(b) b.Top
150 b.Left 100 b.Tag "101"
AddHandler b.Click, New System.EventHandler(A
ddressOf processNewButtonClick) End Sub
12
AddHandler Statement (continued)
Private Sub processNewButtonClick(ByVal sender
As System.Object, ByVal e As System.EventArgs)
Dim myButton As New Button myButton
CType(sender, Button) Label1.Text
CStr(myButton.Tag) End Sub