1. Chapter 3 – Fundamentals of Programming in VB.NET
VB.NET Controls
VB.NET Events
Numbers
Strings
Input and Output
Chapter 3 - VB.NET by Schneider

2. Chapter 3 - VB.NET by Schneider
3.1 VB.NET Controls
Invoking VB.NET
A Text Box Walkthrough
A Button Walkthrough
A Label Walkthrough
A List Box Walkthrough
The Name Property
A Help Walkthrough
Fonts / Auto Hide
Chapter 3 - VB.NET by Schneider

3. Chapter 3 - VB.NET by Schneider
Invoking VB.NET
Chapter 3 - VB.NET by Schneider

4. Chapter 3 - VB.NET by Schneider
Create a New Project
Chapter 3 - VB.NET by Schneider

5. Chapter 3 - VB.NET by Schneider
Initial VB.NET Screen
Chapter 3 - VB.NET by Schneider

6. Chapter 3 - VB.NET by Schneider
A Text Box Walkthrough
In the ToolBox, double click the Text Box icon
The control is selected when you see the sizing handles
Press the Del key to delete
Chapter 3 - VB.NET by Schneider

7. Text Box Properties Categorized view Alphabetical view
Chapter 3 - VB.NET by Schneider

8. Chapter 3 - VB.NET by Schneider
Changing Properties
Chapter 3 - VB.NET by Schneider

9. Chapter 3 - VB.NET by Schneider
ForeColor Property
Chapter 3 - VB.NET by Schneider

10. Chapter 3 - VB.NET by Schneider
Font Property
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11. Chapter 3 - VB.NET by Schneider
A Button Walkthrough
Add the button
Change the Text property
To add the button, double-click on the button icon in the ToolBox, or single click and click and drag
Chapter 3 - VB.NET by Schneider

12. Chapter 3 - VB.NET by Schneider
Add an "access key"
Chapter 3 - VB.NET by Schneider

13. Chapter 3 - VB.NET by Schneider
A Label Walkthrough
Add the Label
Change the Text property
Resize the control
Chapter 3 - VB.NET by Schneider

14. Chapter 3 - VB.NET by Schneider
A List Box Walkthrough
Add the List Box
Change the Text property
Resize the control
Chapter 3 - VB.NET by Schneider

15. Chapter 3 - VB.NET by Schneider
The Name Property
How the programmer refers to a control in code
Name must begin with a letter
Must be less than 215 characters long
May include numbers and the underscore
Use appropriate 3 character naming prefix
Chapter 3 - VB.NET by Schneider

16. Chapter 3 - VB.NET by Schneider
Control Name Prefixes
Chapter 3 - VB.NET by Schneider

17. Chapter 3 - VB.NET by Schneider
Fonts
Proportional width fonts take up less space for "I" than for "W" – like Microsoft Sans Serif
Fixed-width fonts take up the same amount of space for each character – like Courier New
Fixed-width fonts are good for tables
Chapter 3 - VB.NET by Schneider

18. Chapter 3 - VB.NET by Schneider
Auto Hide
Hides tool windows when not in use
Vertical push pin icon indicates auto hide is disabled
Click the push pin to make it horizontal and enable auto hide
Chapter 3 - VB.NET by Schneider

19. Chapter 3 - VB.NET by Schneider
3.2 VB.NET Events
An Event Procedure Walkthrough
Properties and Event Procedures of the Form
The Declaration Statement of an Event Procedure
Chapter 3 - VB.NET by Schneider

20. An Event Procedure Walkthrough
An event is an action, such as the user clicking on a button
Usually, nothing happens until the user does something and generates an event
Chapter 3 - VB.NET by Schneider

21. The three steps in creating a VB.NET program:
Create the interface; that is, generate, position, and size the objects.
Set properties; that is, configure the appearance of the objects.
Write the code that executes when events occur.
Chapter 3 - VB.NET by Schneider

22. Chapter 3 - VB.NET by Schneider
Changing Properties
Properties are changed in code with the following:
controlName.property = setting
This is an assignment statement
txtBox.ForeColor = Color.Red
The setting value on the right hand side of the equal sign is being assigned to the property of the control listed on the left hand side of the equal sign
Chapter 3 - VB.NET by Schneider

23. Chapter 3 - VB.NET by Schneider
Event Procedures
Private Sub objectName_event(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles objectName.event
Shown in the book as:
Private Sub objectName_event(…) Handles objectName.event
Because the book does not make use of the parameter list, it is replaced with an ellipsis
Chapter 3 - VB.NET by Schneider

24. Structure of an Event Procedure
Private Sub objectName_event(...)
Handles objectName.event
statements
End Sub
Chapter 3 - VB.NET by Schneider

25. Chapter 3 - VB.NET by Schneider
Program Region
Chapter 3 - VB.NET by Schneider

26. IntelliSense Automatically pops up to give the programmer help.
Chapter 3 - VB.NET by Schneider

27. Chapter 3 - VB.NET by Schneider
Code for Walkthrough
Private Sub txtFirst_TextChanged(...)
Handles txtFirst.TextChanged
txtFirst.ForeColor = Color.Blue
End Sub
Private Sub btnRed_Click(...)
Handles btnRed.Click
txtFirst.ForeColor = Color.Red
Private Sub txtFirst_Leave(...)
Handles txtFirst.Leave
txtFirst.ForeColor = Color.Black
Chapter 3 - VB.NET by Schneider

28. Assigning properties in code
The following won't work:
Form1.Text = "Demonstration"
The form is referred to by the keyword Me.
Me.Text = "Demonstration"
Chapter 3 - VB.NET by Schneider

29. The Declaration Statement of an Event Procedure
A declaration statement for an event procedure:
Private Sub btnOne_Click(...) Handles btnOne.Click
The name can be changed at will. For example
Private Sub ButtonPushed(...) Handles btnOne.Click
Handling more than one event:
Private Sub ButtonPushed(...) Handles btnOne.Click, btnTwo.Click
btnOne_Click is the name of the event procedure, and btnOne.Click identifies the
event that triggers the procedure
Also, an event procedure can be triggered by more than one event.
Chapter 3 - VB.NET by Schneider

30. Chapter 3 - VB.NET by Schneider
3.3 Numbers
Arithmetic Operations
Variables
Incrementing the Value of a Variable
Built-In Functions:
Math.Sqrt
Int
Math.Round
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31. Chapter 3 - VB.NET by Schneider
Numbers continued
The Integer Data Type
Multiple Declarations
Parentheses
Three Types of Errors
Chapter 3 - VB.NET by Schneider

32. Arithmetic Operations
Numbers are called numeric literals
Five arithmetic operations in VB.NET
+ addition
- subtraction
* multiplication
/ division
^ exponentiation
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33. Chapter 3 - VB.NET by Schneider
Variables
Declaration:
Dim speed As Double
Data type
Variable name
Assignment:
speed = 50
Chapter 3 - VB.NET by Schneider

34. Chapter 3 - VB.NET by Schneider
Initialization
Numeric variables are automatically initialized to 0:
Dim varName As Double
To specify a nonzero initial value
Dim varName As Double = 50
declares a variable named varName to be of type Double. Actually, the Dim statement
causes the computer to set aside a location in memory with the name varName. Since
varName is a numeric variable, the Dim statement also places the number zero in that
memory location. (We say that zero is the initial value or default value of the variable.)
Chapter 3 - VB.NET by Schneider

35. Chapter 3 - VB.NET by Schneider
Incrementing
To add 1 to the numeric variable var
var = var + 1
Or as a shortcut
var +=1
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36. Chapter 3 - VB.NET by Schneider
Built-in Functions
Functions return a value
Math.Sqrt(9) returns 3
Int(9.7) returns 9
Math.Round(2.7) is 3
Chapter 3 - VB.NET by Schneider

37. Chapter 3 - VB.NET by Schneider
Integer Data Type
An integer is a whole number
Declaring an integer variable:
Dim varName As Integer
Chapter 3 - VB.NET by Schneider

38. Multiple Declarations
Dim a, b As Double
Two other types of multiple-declaration statements are
Dim a As Double, b As Integer
Dim c As Double = 2, b As Integer = 5
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39. Chapter 3 - VB.NET by Schneider
Three Types of Errors
Syntax error
Run-time error
Logic error
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40. Chapter 3 - VB.NET by Schneider
3.4 Strings
Variables and Strings
Using Text Boxes for Input and Output
Concatenation
ANSI Character Set
String Properties and Methods:
Length
ToUpper
Trim
ToLower
IndexOf
Substring
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41. Chapter 3 - VB.NET by Schneider
Strings continued
The Empty String
Initial Value of a String
Option Strict
Internal Documentation
Line-Continuation Character
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42. Chapter 3 - VB.NET by Schneider
Variables and Strings
Private Sub btnDisplay_Click(...) Handles btnDisplay.Click
Dim today As String
today = "Monday"
With lstOutput.Items
.Clear()
.Add("hello")
.Add(today)
End With
End Sub
Chapter 3 - VB.NET by Schneider

43. Using Text Boxes for Input and Output
The contents of a text box is always a string
Input example
strVar = txtBox.Text
Output example
txtBox.Text = strVar
Chapter 3 - VB.NET by Schneider

44. Data Conversion
Because the contents of a text box is always a string, sometimes you must convert the input or output
numVar = CDbl(txtBox.Text)
txtBox.Text = CStr(numVar)
Converts a String to a Double
Converts a number to a string
Chapter 3 - VB.NET by Schneider

45. Chapter 3 - VB.NET by Schneider
Concatenation
Combining two strings to make a new string
quote1 = "The ballgame isn't over, "
quote2 = "until it's over."
quote = quote1 & quote2
txtOutput.Text = quote & " Yogi Berra"
Displays
The ball game isn't over until it's over. Yogi Berra
Chapter 3 - VB.NET by Schneider

46. Chapter 3 - VB.NET by Schneider
ANSI Character Set
A numeric representation for every key on the keyboard
Chapter 3 - VB.NET by Schneider

47. String Properties and Methods:
"Visual".Length is 6.
"Visual".ToUpper is VISUAL.
"123 Hike".Length is 8.
"123 Hike".ToLower is 123 hike.
"a" & " bcd ".Trim & "efg" is abcdefg.
Chapter 3 - VB.NET by Schneider

48. More String Properties and Methods:
"fanatic".Substring(0, 3) is "fan".
"fanatic".IndexOf("ati") is 3.
"fanatic".Substring(4, 2) is "ti".
"fanatic".IndexOf("a") is 1.
"fanatic".Substring(4) is "tic".
"fanatic".IndexOf("nt") is –1.
Chapter 3 - VB.NET by Schneider

49. Chapter 3 - VB.NET by Schneider
The Empty String
The string "", which contains no characters, is called the empty string or the zero-length string.
The statement lstBox.Items.Add("") skips a line in the list box.
The contents of a text box can be cleared with either the statement
txtBox.Clear()
or the statement
txtBox.Text = ""
Chapter 3 - VB.NET by Schneider

50. 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"
Chapter 3 - VB.NET by Schneider

51. Chapter 3 - VB.NET by Schneider
Option Strict
VB.NET allows numeric variables to be assigned strings and vice versa, a poor programming practice.
To turn this feature off, put the following statement at the very top of the code window
Option Strict On
Chapter 3 - VB.NET by Schneider

52. Internal Documentation
Other people can easily understand the program.
You can understand the program when you read it later.
Long programs are easier to read because the purposes of individual pieces can be determined at a glance.
Chapter 3 - VB.NET by Schneider

53. Line-Continuation Character
A long line of code can be continued on another line by using underscore (_) preceded by a space
msg = "640K ought to be enough " & _
"for anybody. (Bill Gates, 1981)"
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54. Chapter 3 - VB.NET by Schneider
3.5 Input and Output
Formatting Output with Format Functions
Formatting Output with Zones
Reading Data from Files
Getting Input from an Input Dialog Box
Using a Message Dialog Box for Output
Chapter 3 - VB.NET by Schneider

55. Formatting Output with Format Functions
String Value
FormatNumber( ,1)
12,345.6
FormatCurrency( ,2)
$12,345.63
FormatPercent(0.185,2)
18.50%
Chapter 3 - VB.NET by Schneider

56. Formatting Output with Zones
Use a fixed-width font such as Courier New
Divide the characters into zones with a format string.
Dim fmtStr As String = "{0, 15}{1, 10}{2, 8}"
lstOutput.Items.Add(String.Format(fmtStr, data0, data1, data2))
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57. Chapter 3 - VB.NET by Schneider
Inputting Data
Data can be stored in files and accessed with a StreamReader object or supplied by the user with an input dialog box.
Chapter 3 - VB.NET by Schneider

58. Steps to Use StreamReader
Execute a statement of the form
Dim readerVar As IO.StreamReader = _
IO.File.OpenText(filespec)
or the pair of statements
Dim readerVar As IO.StreamReader
readerVar = IO.File.OpenText(filespec)
Assume the file contains one item of data per line.
Read items of data in order, one at a time, from the file with the ReadLine method.
strVar = readerVar.ReadLine
After the desired items have been read from the file, terminate the communications link
readerVar.Close()
1. Execute a statement of the form
Dim readerVar As IO.StreamReader
A StreamReader is an object from the Input/Output class that can read a stream of
characters coming from a disk or coming over the Internet. The Dim statement
declares the variable readerVar to be of type StreamReader.
2. Execute a statement of the form
readerVar = IO.File.OpenText(filespec)
where filespec identifies the file to be read. This statement establishes a communi-cations
link between the computer and the disk drive for reading data from the disk.
Data then can be input from the specified file and assigned to variables in the pro-gram.
This assignment statement is said to “open the file for input.”
Just as with other variables, the declaration and assignment statements in Steps
2 and 3 can be combined into the single statement
Dim readerVar As IO.StreamReader = IO.File.OpenText(filespec)
3. Read items of data in order, one at a time, from the file with the ReadLine method.
Each datum is retrieved as a string. A statement of the form
strVar = readerVar.ReadLine
causes the program to look in the file for the next unread line of data and assign it
to the variable strVar. The data can be assigned to a numeric variable if it is first
converted to a numeric type with a statement such as
numVar = CDbl(readerVar.ReadLine)
Note: If all the data in a file have been read by ReadLine statements and another item
is requested by a ReadLine statement, the item retrieved will have the value Nothing.
4. After the desired items have been read from the file, terminate the communications
link set in Step 3 with the statement
readerVar.Close()
Chapter 3 - VB.NET by Schneider

59. 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")
Chapter 3 - VB.NET by Schneider

60. Using a Message Dialog Box for Output
MsgBox(prompt, , title)
MsgBox("Nice try, but no cigar.", , "Consolation")
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")
Chapter 3 - VB.NET by Schneider