VB.Net Introduction

1. VB.Net Introduction

2. .NET Framework • .NET Framework class libraries: A large set of classes that forms the basis for objects that can be used programmatically. • Programming in the .NET Framework means making use of the classes exposed by the Framework, building your own classes on top of these and manipulating the resulting objects. • Creating Internet applications and Windows applications

3. Class and Object • A class is a blueprint from which objects are made. Every object created from a class is an instance of the class. • Properties and methods: An object’s interface consists of properties and methods. A property is an attribute associated with an object, while a method is an action that the object can carry out.

4. VB.NET is Object-Oriented • Everything from the simplest data types provided by VB to the complex windows is a class. • Ex: • Dim iNum as Integer • iNum=10 • Debug.WriteLine (“The number is: “ & iNum.ToString)

5. Visual Studio .NET • It is the development environment for creating applications based on the .NET Framework. • It supports VB, C#, and C++. • Demo: • Start page: MyProfile • Starting project: Project types, name and location, • Solutions and projects, renaming a project, solution explorer, property page, AutoHide, Dock/Float • Configure start up environment: Tools/Option • View/Solution, View/Class, Project/Add Windows Form, Project/Add New Item • Form, Code view, File Properties and Object properties

6. 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 control has a number of events that it can respond to. Typical events include clicking a mouse button, type a character on the keyboard, changing a value, etc. • Event procedure

7. Typical VB.Net Controls • Form design view: ToolBox/Windows Forms • TextBox • Label • Button • CheckBox • RadioButton • ListBox • ComboBox • PictureBox • Etc.

8. Form • Properties: • Name, FormBorder, Text, BackColor, BackImage, Opacity? • Events: • Load, Closed • Rename a form(hard to to): • Change the name and text property. • Rename the form in the Solution Explorer. • Change the StartUp in the Project Property. • Change the name in the code window.

9. Text Box • Properties: • AutoSize, BorderStyle, CauseValidation, Enabled, Locked, Multiline, PasswordChar, ReadOnly, ScrollBar, TabIndex, Text, Visible, etc. • Events: • CauseValidation, TextChanged, etc. • To refer to a property: • ControlName.PropertyName • Ex. TextBox1.Text • Properties can be set at the design time or at the run time with code. • Demo: TextAlignment

10. Label • Display message, output • Property: • Text, TextAlign • Autosize • Visible • Button • Click event

11. Typical VB.Net Programming Tasks • Creatin g 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.

12. Demo Num1 Num2 Sum = Control properties Event: Click, MouseMove, FormLoad, etc. Event procedures Sum: textBox3.text=CStr(CDbl(textBox1.text)+CDbl(textBox2.text)) Or (CDbl(textBox1.text)+CDbl(textBox2.text)).toString Challenge: How to draw a horizontal line?

13. VB Projects • A VB project consists of several files. Visual Studio .Net automatically creates a project folder to keep all project files in the folder. • Solution file • Project file • Form file • Modules • Class file • Etc.

14. Configure VB Project • Project property page • General • Build: • Option Explicit: On – must declare variables • Option Strict: Off – VB will automatically convert data if necessary • Option compare: Binary – case sensitive • Imports

15. Variable Declarations • 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

16. 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.

17. 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

18. 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

19. Variable Default Value • Variables with a numeric data type: 0 • Boolean variables: False • Date variables: 12:00:00 AM, January 1 of the year 1. • String variables: Nothing

20. 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” • MsgBox(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 class or module variable (variable declared in a Module) declared with the Public keyword.

21. 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 • Ex. System.Convert.ToDateTime(var) • Type class’s methods: • toString • Demo: Val

22. 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#

23. 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

24. Some Date Functions • Now: Current date and time • Today: Current date • TimeOfDay • DateDiff • Demo • Days to Christmas • Date data type properties and methods

25. Arithmetic and String Operators • +, -, *, / , ^, ( ) • \:Integer division • Return integer result • If the operands are real numbers, they are rounded to the nearest whole number before the division takes place. • Mod: • Remainder = 17 mod 5 • Order of evaluation: • 1. ( ), 2. ^, 3.*, /, 4.\, 5.Mod, 6.+, - • String Concatenation: &, + • Compound operator: : X= X+1 or X +=1

26. Demo • Chap 3, simple calculator