CS 2340: Programming in VB

Lab 2

Due 9 pm, Friday, September 14

1

Button Access Key (Hot Key)

Put a “&” in button text

The char after “&” is underlined and becomes the Access Key

Example

Text of btnExit: EXIT (E&XIT)

[ALT] + X ==> the same as click btnExit

2

Form Properties

• Text (title) • FormBorderStyle • WindowsState: Normal, Minimized, Maximized • StartPosition • ControlBox: Control buttons

Minimize, Maximize (restore), Close• MinimizeBox, MaximizeBox

3

Form Properties

• Button Click Event

Pressing ENTER when a button has the focus• Multiple buttons on a form• AcceptButton:

Pressing ENTER when no button has the focus• CancelButton

Pressing ESC when no button has the focus• Different ways to invoke the button click event

4

Invoking Event Procedures

Private Sub btnExit_Click(...) Handles btnExit.Click

End

End Sub

' It will not work if Handles is removed.

Private Sub btnExit_Click(...)

End

End Sub

‘ You could change the Sub’s name

Private Sub SubExit(...) Handles btnExit.Click

5

Function Format and FormatCurrency

txtSum.Text = Format(result, "Currency")

txtSum.Text = Format(result, "C")

txtSum.Text = Format(result, "General Number")

txtSum.Text = Format(result, “n")

txtSum.Text = Format(result, "Percent")

txtSum.Text = Format(result, "P")

txtSum.Text = Format(result, "Standard")

txtGrossPay.Text = FormatCurrency(gross)

6

Message Box

Method Show

Overloaded

Help

Manage Help Settings

View Help

7

Message Box

MessageBoxIcon

•Asterisk

•Error

•Exclamation

•Hand

•Information

•None

•Question

•Stop

•Warning

8

String on Multiple Lines' Special char vbCrLf

MessageBox.Show("Invalid Hours!" + vbCrLf + _

"Hours must be non-negative!", _

"Lab 2", MessageBoxButtons.OK, MessageBoxIcon.Error)

' Special integer Keys.LineFeed

' Run time error

MessageBox.Show("Invalid Hours!" + Keys.LineFeed + _

"Hours must be non-negative!", _

"Lab 2", MessageBoxButtons.OK, MessageBoxIcon.Error)

' Special integer Keys.LineFeed

' Cast function Chr

MessageBox.Show("Invalid Hours!" + Chr(Keys.LineFeed) + _

"Hours must be non-negative!", _

"Lab 2", MessageBoxButtons.OK, MessageBoxIcon.Error)

9

GUI Programs

Three Steps

Input (from controls)

Process (no controls)

Output (to controls)

10

Click Event Procedure for btnCompute

‘ Declare variables Dim rate, hours, grossPay, deduction, netPay As Double Dim input As String

‘ Check ID input = txtID.Text.Trim() . . .

‘ Check Rate input = txtRate.Text.Trim() . . .

‘ Check Hours input = txtRate.Text.Trim() . . .

‘ Process ‘ No more controls!

' Display results using controls

11

Lab 2: Checking Rateinput = txtRate.Text.Trim()

If IsNumeric(input) And _ InStr(input, "e", CompareMethod.Text) = 0 Then rate = Convert.ToDouble(input) If rate <= 0 Then MessageBox.Show("Invalid Rate!" + vbCrLf & _ "Rate must be positive!", "Lab 2", _ MessageBoxButtons.OK, MessageBoxIcon.Warning) txtRate.Focus() Exit Sub End IfElse MessageBox.Show("Invalid Rate!" + Chr(Keys.LineFeed) & _ "Rate must be a number!", "Lab 2", _ MessageBoxButtons.OK, MessageBoxIcon.Warning) txtRate.Focus() Exit SubEnd If

12

Testing GUI Programs

COURSE OUTCOMES• . . .• Design, develop and test Visual Basic programs.

Users can enter whatever they want and in what order they like.

We must make sure the program won’t crash and always work correctly!

13

Lab 2: Testing ID

• Empty ID

Error message

• Spaces only

Error message

• String “CS 2340”

Good ID

• String “ CS 2340 ”

Good ID

14

Positive and Negative

• Zero is a positive number.

True False

• Zero is a negative number.

True False

• Zero is a non-positive number.

True False

• Zero is a non-negative number.

True False

15

Lab 2: Testing Rate (positive)• Empty rate

Error message

• Not a number such as “cs2340” or 234cs

Error message

• Scientific notation “2e3”

Error message

• Scientific notation “2E-3”

Error message

• Number 0

Error message

• Negative number such as -1

Error message

• Positive number 10.45

Good Rate! 16

Lab 2: Testing Hours (non-negative)

• Similar to testing rate

• Negative number such as -1

Error message

• Positive number 10.45

Good Rate!

• Number 0

Good Hours!

Hours can be zero!

17

Lab 2: Testing Gross Pay

• Rate: 10 Hours 20

Gross Pay: 200

• Rate: 10 Hours 40

Gross Pay: 400

• Rate: 10 Hours 50

Gross Pay: 500?

Gross Pay: 550?

18

Schedule

Lab 2: Due 9pm, Friday, September 14

No Grace Time!

Test 1: Friday, September 21

Based on Lab1 and Lab2

19

Test 1• Friday, September 21

• Lab 206

• Create a VB.NET program within 52 minutes

• 20 points

• Open book and notes

• Online help available

• Your labs available

• Do it yourself

• No email

• No discussion

• No credit if no executable file or it does not run

• You can ask me for help, but you may lose 3 points each time you receive help

• You cannot ask me any questions during the last 15 minutes of the test!

• -3 for each run time error

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