Assignment 10.1: Decision-Making

Week 9 and 10
1. Decision making (Selection Structure)
2. Often used comparison operators: (pp. 199-200)

3. If statements: single-alternative, dual-alternative, and multiple-alternative. (192-198, 276-278)
a. If / End If statement
If [evaluating a condition] Then
[Some code are executed if True] End If
b. If / Else /End If statement
If [evaluating a condition] Then
[Some code are executed if True]
Else
[Other code are executed if False]
End If

c. If / ElseIf .. /End If statement (When you have more than two selections, pp. 275-278.)
If [evaluating a condition] Then
[Some code are executed]
ElseIf [evaluating second condition] Then
[Other code are executed. You may have as many ElseIf sections as you
need. ]
Else
[Other code are executed]
End If

4. TryParse function (128-129, 219-220): Integer.TryParse, Single.TryParse, Long.TryParse and other types of TryParse function. This function requires two arguments, a string and a numeric variable. It does two things:
A. It returns a Boolean value, depending on whether it succeeds in converting a string to a numeric value.
B. It assigns a value to its second argument, either a converted numeric value or, in not convertible, zero.

Understand why TryParse function is more useful than Val () function
Here is an example where TryParse Function is used to verify user entry. If Double.TryParse(txtSales.Text, dblSale) Then (Some code here………) Else MessageBox.Show("Wrong sales amount. Try again.") End If

5. ToUpper and ToLower methods (215-218)
Projects: SelectionIf
GUI (when debugging)

Project Selection Code:

Code for btnTryParse

Code btnDriverLicense

Assignment 1: Ticket Price.
Pseudo code for btnTicket:
Ask user to type S, C or other letter for a senior, a child, or anyone else;
If senior, ask to pay $5; if child, free; other people, $10

Assignment 2: Vending machine
Pseudo code for btnVendingMachine
Ask user to type a number:
10 for Pepsi; 15 for Coca Cola; 18 for Snapple; 22 for Ginger Ale; 30 for Gatorade
If user types 10, txtDisplay will show “You got a Pepsi!” …….
If user types a wrong number, txtDisplay will show “ …. does not exist. Try again.”
Tip:
1. Treat numbers as strings in this project because they are not used for calculation.
2. No need to use ToUpper or ToLower method because numeric strings don’t have case.