1. Additional Topics in VB.NET
Lecture 9
Additional Topics in VB.NET

2. Timer Control Invisible during runtime
Triggers an event after a specified period of time
The Interval property specifies the time period – measured in milliseconds
To begin timing, set the Enabled property to True
To stop timing, set the Enabled property to False
The event triggered each time is called Tick event

3. Timer Control (cont.) Interval property Enabled property Tick event
Between 0 and 65,535 milliseconds
1,000 milliseconds = 1 second
Enabled property
False (default) ==> Do not run Tick event
True ==> Run Tick event at designated interval
Tick event
Runs each time the Timer's designated interval elapses, if Enabled = True

4. DateTimePicker & Calendar Controls
Takes less screen space
Displays only day and date unless user drops down the calendar
MonthCalendar
Displays calendar
Provide the ability to display calendars on your form

5. Calendar Controls (cont.)
DateTimePicker
MonthCalendar

6. Getting Input from an Input Dialog Box
stringVar = InputBox(prompt, title)
fileName = InputBox("Enter the name " _
& "of the file containing the " & _
"information.", "Name of File")

7. Using a Message Dialog Box for Output
Displays a message in a dialog box,
waits for the user to click a button
MsgBox(prompt)
MsgBox("Nice try, but no cigar")
MsgBox(prompt, , title)
is executed, where prompt and title are strings, a message dialog box appears with prompt
displayed and the title bar caption title and stays on the screen until the user presses
Enter, clicks on the box in the upper-right corner, or clicks OK. For instance, the state-ment
MsgBox("Nice try, but no cigar.", , "Consolation")

8. Some Built-In Functions
Example
Input
Output
Int
Int(2.6) is 2
number
Chr
Chr(65) is “A”
string
Asc
Asc(“Apple”) is 65
Math.Round
Math.Round(2.7) is 3
Math.Sqrt
Math.Sqrt(9) is 3
Number
number

9. Built-in Functions (2) Functions return a value
IsNumeric(9) ' Returns True
IsNumeric(459.95) ' Returns True
IsNumeric(“45 help”) ' Returns False

10. Input Validation
Code If structure to determine if value falls within a range of acceptable values
Refer to lab 6 – Calculate Grade
Use single If for each value, Else for message to user, and execute Focus Method to reset focus to text box

11. Input Validation (2)
Check to see if valid values were entered by user in TextBox and use Message Box to notify user if invalid
IsNumeric function checks for numeric values
If IsNumeric(txtQuantity.Text) Then ...
Check for required data or not blank
If txtName.Text <> "" Then ...

12. Variables Declaration: Assignment: Dim speed As Double speed = 50
Data type
Variable name
Assignment:
speed = 50

13. Initial Value of a Integer
An integer is a whole number
Declaring an integer variable:
Dim varName As Integer
(Numeric variables are automatically initialized to 0)
To specify a nonzero initial value
Dim varName As Double = 50

14. Initial Value of a String
By default the initial value is Nothing
Strings can be given a different initial value as follows:
Dim today As String = "Monday"

15. Incrementing To add 1 to the numeric variable var Or as a shortcut
var = var + 1
Or as a shortcut
var +=1

16. Multiple Declarations
Dim a As Integer
Dim b As Integer
Alternative method: Multiple-declaration
Dim a, b As Integer

17. ' Display the Hello World message
Remark Statement
Also known as Comment, used for documentation
Non-executable
Automatically colored Green in Editor
Begins with an apostrophe ( ' )
On a separate line from executable code
At the right end of a line of executable code
' Display the Hello World message

18. lblMessage.Text=" Hello World "
Assignment Statement
Assigns a value to a property or variable
Operates from right to left
Enclose text strings in quotation marks (" ")
lblMessage.Text=" Hello World "