1. VB.Net Introduction

2. Visual Studio 2008 It supports VB.Net, J#, C#, and C++. Demo: –Start page: Recent projects –Starting project: File/New Project/Project types: Windows Application –View: Solution Explorer/Data Sources Server Explorer Property Window ToolBox –Form design view/Form code view –Tools/Option –Environment –Projects and Solutions »VB defaults –Project/Add New Item –Project properties: Right-click project name and choose Properties Start Up form –Property window example

3. Introduction to Visual Basic.Net Event-driven programming –The interface for a VB program consists of one or more forms, containing one or more controls (screen objects). –Form and controls have events that can respond to. Typical events include clicking a mouse button, type a character on the keyboard, changing a value, etc. –Event procedure

4. Form Properties: –Name, FormBorderStyle, Text, BackColor, BackImage, Opacity Events: –Load, FormClosing, FormClosed –GotFocus, LostFocus –MouseHover, Click, DoubleCLick

5. Typical VB.Net Controls TextBox Label Button CheckBox RadioButton ListBox ComboBox PictureBox

6. Text Box Properties: –AutoSize, BorderStyle, CauseValidation, Enabled, Locked, Multiline, PasswordChar, ReadOnly, ScrollBar, TabIndex, Text, Visible, WordWrap, etc. Properties can be set at the design time or at the run time using code. To refer to a property: –ControlName.PropertyName –Ex. TextBox1.Text –Note: The Text property is a string data type and automatically inherits the properties and methods of the string data type.

7. Typical VB.Net Programming Tasks Creating the GUI elements that make up the application’s user interface. –Visualize the application. –Make a list of the controls needed. Setting the properties of the GUI elements Writing procedures that respond to events and perform other operations.

8. Demo Num1 Num2 Sum =.Control properties.Event: Click, MouseMove, Form Load, etc..Event procedures Sum: textBox3.text=CStr(CDbl(textBox1.text)+CDbl(textBox2.text)) Or (CDbl(textBox1.text)+CDbl(textBox2.text)).toString.Demo: Text alignment (TextAlign property)

9. Configure VB Project Project property page –Application –Compile –References Tools/Options –Environment –Projects and Solutions »VB defaults

10. VB Defaults Option Explicit: –On --- must declare variables before use Option Strict: –Off --- VB will convert the data Option Compare: –Binary --- case sensitive –Text --- case insensitive Option Infer –On --- When you set Option Infer to On, you can declare variables without explicitly stating a data type. The compiler infers the data type of a variable from the type of its initialization expression.

11. Variable Declarations Option Explicit Dim variableName as DataType Variable naming rules: –The first character must be a letter or an underscore character. –Use only letters, digits, and underscore. –Cannot contain spaces or periods. –No VB keywords Naming conventions: –Descriptive –Consistent lower and upper case characters. Ex. Camel casing: lowerUpper, employeeName

12. Control Naming Conventions The first three letters should be a lowercase prefix that indicates the control’s type. –frm, txt, lbl, btn. The first letter after the prefix should be uppercase. –txtSalary, lblMessage The part of the control name after the prefix should describe the control’s purpose in the application.

13. VB Data Types Boolean (True/False):2 bytes Byte: Holds a whole number from 0 to 255. Char: single character Date: date and time, 8 bytes. Decimal: Real number up to 29 significant digits, 16 bytes Double: real, 8 bytes Single: real, 4 bytes Integer: 4 bytes(int32, uint32) Long: 8 bytes integer Short: 2 bytes integer String Object: Holds a reference of an object

14. Variable Declaration Examples Dim empName as String Declare multiple variables with one Dim: –Dim empName, dependentName, empSSN as String Dim X As Integer, Y As Single Initiatialization –Dim interestRate as Double = 0.0715

15. Variable Scope Block-level scope: declared within a block of code terminated by an end, loop or next statement. –If city = “Rome” then Dim message as string = “the city is in Italy” MessageBox.Show(message) –End if Procedural-level scope: declared in a procedure Class-level, module-level scope: declared in a class or module but outside any procedure with either Dim or Private keyword. Project-level scope: a module variable declared with the Public keyword.

16. Data Conversion Implicit conversion: When you assign a value of one data type to a variable of another data type, VB attempts to convert the value being assigned to the data type of the variable if the OptionStrict is set to Off. Explicit conversion: –VB.Net Functions: CStr, Ccur, CDbl, Cint, CLng, CSng, Cdate,Val, etc. –.Net System.Convert Type class’s methods: –toString

17. Date Data Type Variables of the Date data type can hold both a date and a time. The smallest value is midnight (00:00:00) of Jan 1 of the year 1. The largest value is 11:59:59 PM of Dec. 31 of the year 9999. Date literals: A date literal may contain the date, the time, or both, and must be enclosed in # symbols: –#1/30/2003#, #1/31/2003 2:10:00 PM# –#6:30 PM#, #18:30:00# Note: ControlPanel/RegionalOptions/Date

18. Date Literal Example: –Dim startDate as dateTime –startDate = #1/30/2003# Use the System.Convert.ToDateTime function to convert a string to a date value: –startDate = System.Convert.ToDateTime(“1/30/2003”) –If date string is entered in a text box: startDate = System.Convert.ToDateTime(txtDate.text) Or startDate=Cdate(txtDate.text) Date data type format methods

19. Some Date Functions Now: Current date and time Today: Current date TimeOfDay DateDiff: Demo –Days between two dates –Days to Christmas DateDiff(DateInterval.Day, Today(), #12/25/2009#) –Date data type properties and methods

20. Using Online Help Example:Search Help for DateDiff MSDN VB Developer Center –http://msdn.microsoft.com/en- us/vbasic/default.aspx –Library/Visual Studio/Visual Basic Reference –Language reference »Functions: » DateDiff Function »Statements

21. Arithmetic and String Operators +, -, *, /. \, ^ String Concatenation: &, + Compound operator: : X= X+1 or X +=1

22. The If … Then Statement If condition Then Statements End If If condition Then Statements Else Statements End If Condition: –Simple condition: Comparison of two expressions formed with relational operators:>,, >=, <= Boolean variable –Complex condition: Formed with logical operators: ( ), Not, And, Or

23. Complex Condition If 12<=Age<=65 Then Fee = 20, else Fee = 5 Admission rules: Applicants will be admitted if meet one of the following conditions: –GPA>3.0 –GPA>2.5 AND SAT >700 Scholarship rules: Meet all the conditions: –GPA>3.2 –Must be Accounting or CIS Admission rules: Applicants will be admitted if meet all the following conditions: –SAT>700 Or Income > 40000 –Not GPA < 2.5

24. IF Statement IF condition THEN statements [ELSEIF condition-n THEN [elseifstatements] [ELSE [elsestatements]]] End If

25. Using Boolean Variables as Flags A flag is a Boolean variable that signals when some condition exists in the program. Dim goodStudent as Boolean=True If daysAbsent > 10 Then goodStudent = False End if If goodStudent Then TextBox1.text=“Good Student” Else textBox1.text=“Not good student” End If

26. Select Case Structure SELECT CASE testexpression [CASE expressionlist-n [Statements] [CASE ELSE [elsestatements] END SELECT

27. Select Case Example SELECT CASE temperature CASE <40 Text1.text=“cold” CASE < 60 Text1.text=“cool” CASE 60 to 80 Text1.text=“warm” CASE ELSE Text1.text=“Hot” End Select

28. The Expression list can contain multiple expressions, separated by commas. Select Case number Case 1, 3, 5, 7, 9 textBox1.text=“Odd number” Case 2, 4, 6, 8, 10 textBox1.text=“Even number” Case Else End Select

29. Loop FOR index – start TO end [STEP step] [statements] [EXIT FOR] NEXT index DO [{WHILE| UNTIL} condition] [statements] [EXIT DO] LOOP

30. Example: Display characters entered in textbox1one at a time Dim index As Integer index = 0 For index = 0 To TextBox1.Text.Length - 1 MessageBox.Show(TextBox1.Text.Substring(index, 1)) Next Problem : How many “a” entered in textbox1?

31. Do While/Do Until Private Sub Command1_Click() Dim counter As Integer counter = 0 Do While counter <= 5 Debug.write(counter) counter = counter + 1 Loop Text1.Text = counter End Sub Private Sub Command2_Click() Dim counter As Integer counter = 0 Do Until counter > 5 Debug.write(counter) counter = counter + 1 Loop Text1.Text = counter End Sub

32. With … End With With TextBox1.Height = 250.Width = 600.Text = “Hello” End With Convenient shorthand to execute a series of statements on a single object. Within the block, the reference to the object is implicit and need not be written.

33. Procedures. Sub procedure: Sub SubName(Arguments) … End Sub –To call a sub procedure SUB1 CALL SUB1(Argument1, Argument2, …)

34. Function Private Function tax(salary) As Double tax = salary * 0.1 End Function –Or Private Function tax(salary) Return salary * 0.1 End Function

35. Call by Reference Call by Value ByRef –The address of the item is passed. Any changes made to the passing variable are made to the variable itself. ByVal –Default –Only the variable’s value is passed.

36. ByRef, ByVal example Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim myStr As String myStr = TextBox1.Text Call ChangeTextRef (myStr) TextBox1.Text = myStr End Sub Private Sub ChangeTextRef(ByRef strInput As String) strInput = "New Text" End Sub