VB.NET

1. VB.NET Professor Corinne Hoisington Central Virginia Community College

2. Programming Curricular Changes • Why should we implement this new software developer’s tool? • What language will be “THE” most used language? • Is this simply another upgrade? • What classes could incorporate the content of .NET?

3. Visual Basic.NET • Easier to Use • Streamlined and Modernized • More Powerful than VB 6.0 • Higher level of access to system resources that in the past required the use of languages like C++ • True Object Inheritance • Garbage Collection for better memory management

4. Visual Studio .NET 2003 • Released April 27, 2003 • J# • Mobile Web Applications: using the integrated ASP.NET Web Forms and the Visual Studio .NET Web Forms Designer, Visual Basic and C# developers can easily build thin-client Web-based applications that render intelligently on more than 200 devices, including wireless application protocol (WAP) phones, wireless personal digital assistants (PDAs), and pagers.

5. New Web Development • Programming for the Web vs. Windows • New set of controls • Web page layout • ASP.NET • ADO.NET • Mobile Applications • Convert Projects

6. Just an Upgrade??? • NO! • VB.NET omits quite a few forms of syntax • VB.NET requires a total rewrite rather than a simple port of code • VB.NET is not dependent on older libraries such as VBA runtime and ADO (ActiveX Database Object)

7. A new Forms Engine • The forms engine has been replaced by the forms engine built into .NET • This new forms engine is called Windows Forms (or Win Forms for short) • Win Forms add such features as docking and opacity

8. Forms are now Classes • In VB6, forms were classes, but you rarely treated them that way • VB .NET shows the code that instantiates the form • To show additional forms, you must first instantiate them

9. Form Changes • Forms have undergone a number of changes. These include: • The Forms engine is now WinForms • Forms are classes • A Component Tray holds non-visual controls at design-time

10. VB.NET or C#.NET • C# is a new language that was designed to be friendly to programmers who are already proficient in C or C++ • Either language can be used to write software that takes full advantage of the CLR and .NET framework

11. NEW IDE

12. New Tools • Calendar Tool • Date Picker Calendar • Opacity Control • Timer does not lay on form • Command Buttons are now called Buttons • Use “btn” for prefix

13. Great New Menu Tool

14. More Changes • The Editor window (formerly the Code window) • Lots more IntelliSense help; can be confusing • Declarations section replaces General Declarations • Collapsible Regions in code (Plus signs)

15. Collapsed Regions Tabs Method List Class List Collapsed Region Collapsed Procedure

16. General Changes • There have been a number of changes in VB .NET. General changes include: • Form changes • Option Strict • Event Handler changes • Default Properties • Calling Subs and Functions • Boolean operators • Using CTRL + Space to finish variables

17. The Component Tray • In VB6, controls that were only visible at design-time still appeared on the form in the IDE • Such as the Timer control • VS .NET places controls that are invisible at runtime in a small area below the form • This area is the Component Tray

18. A new Forms Engine • The forms engine has been replaced by the forms engine built into .NET • This new forms engine is called Windows Forms (or Win Forms for short) • Win Forms add such features as docking and opacity

19. Forms are now Classes • In VB6, forms were classes, but you rarely treated them that way • VB .NET shows the code that instantiates the form • To show additional forms, you must first instantiate them

20. The Component Tray • In VB6, controls that were only visible at design-time still appeared on the form in the IDE • Such as the Timer control • VS .NET places controls that are invisible at runtime in a small area below the form • This area is the Component Tray

21. Calls to Subs and Functions Require Parentheses • In VB6, you called a Sub without parentheses AddOrder OrderNum, OrderDate • You could use the Call statement, which required parenthese Call AddOrder(OrderNum, OrderDate) • .NET always requires parentheses for a Sub, as well as with Functions

22. New Boolean Operators • The And and Or keywords do not short-circuit in VB and VB .NET • Both sides of an operator are evaluated, even if the first option invalidates the statement • VB .NET adds two short-circuiting Boolean operators: • AndAlso • OrElse

23. Boolean Operators Example Dim x As Integer x = 0 If x>2 And 5\x > 1 Then ... • This If statement is already false on the x>2 part, but 5\x is still checked because And does not short-circuit • In this case, 5\x causes a “divide by zero” error

24. Boolean Operators Example cont. Dim x As Integer x = 0 If x>2 AndAlso 5\x > 1 Then ... • This If statement is already false on the x>2 part, so the AndAlso does not check the 5\x portion • The key result: No Error!

25. The Value of True • The value of True has not changed • Originally, the value of True was going to change, but it did not • The value of True in VB .NET is still negative one (-1) • Your code should not check for -1, but for True

26. Common Language Runtime • VB.NET has undergone a significant overhaul to accommodate the CLR • New object oriented design features • Much higher levels of type safety • Universal type system allows for greater inoperability

27. Changes in Properties • The Alignment property becomes TextAlign • The maximum length of identifiers is 16,383 • All new Help — MSDN • OptionButton becomes RadioButton • Frame becomes GroupBox • New component tray holds non-visible controls

28. More Property Changes • Text boxes have a Clear method txtName.Clear() txtName.Text = “” • Focus method replaces SetFocus txtName.Focus() • Many colors available through the Color class • lblMessage.ForeColor = Color.Blue Color.Aquamarine Color.Bisque Color.Chocolate Color.Cadetblue

29. Tab Order This is neat! Click on View and Tab Order

30. Caption / Text Property • VB 6.0 - Some controls, such as Label, have a Caption property that determines the text displayed in or next to the control. Other controls, such as TextBox, have a Text property that determines the text contained in the control • VB.NET - In Windows Forms, the property that displays text in a control is consistently called Text on all controls. This simplifies the use of controls.

31. Data Types

32. More Integer Data Types

33. Other Data Types

34. Block-Level Scope • VB .NET introduces variables that only exist within blocks of code • Blocks are items such as For…Next, Do…Loop, and If Then…End If • Variables are only visible within the block, but their lifetime is that of the whole procedure

35. Changes in Syntax • Firstly the ‘Currency’ data type is no longer used in VB 6.0 • Currency has been replaced with Decimal in VB.NET • The Currency data type (64 bit) does not provide sufficient accuracy to avoid rounding errors, so Decimal (96 bit) was created as its own data type. • Dim x As Currency is upgraded to: Dim x As Decimal

36. Long and Integer Data Types • VB 6.0 - Long variables were stored as 32-bit numbers and Integer variables as 16-bit numbers • VB.NET - Long variables are stored as 64-bit numbers, Integer variables are stored as 32-bit numbers, and Short variables are stored as 16-bit numbers.

37. No More Variant Data Type • Variant data types are changed to Object due to keeping all the languages more similar. This is no longer the same as a pointer to an object. • Dim x As Variant is upgraded to: Dim x As Object

38. Option Explicit • In VB.BET the option is turned on by default for all new projects. • When Option Explicit Off is used (not a good programming style), you can use any variable without first declaring it.

39. Option Strict On • New Option in VB.NET • When Option Strict is turned on, the compiler/editor does not allow implicit conversions from a wider data type to a narrower one, or between String and numeric data types • CInt and CDec convert • Limits erroneous numbers or run-time errors • Place the line Option Strict On before the first line of code

40. Converting Data Types • Initialize a variable at declaration Dim intMax As Integer = 100I Dim decRate As Decimal = 0.08D • Declare multiple variables at once Dim intCount, intNum As Integer • Convert all input to correct data type (Do not use Val function) decSale = CDec(txtSale.Text) • CInt (still rounds to even #) • CDec • CStr ** CInt and CDec parse some characters like $, commas,()

41. Format • VB 6.0 – Format(variable, “Currency”) • VB.NET – FormatCurrency(variable) FormatPercent(variable) FormatNumber(variable) FormatNumber(variable,3) FormatDateTime(variable)

42. New Compound Operators • New assignment Operators • += –= *= /= \= &= • decTotal += decSale same as decTotal=decTotal + decSale

43. Case Conversions • String ToUpper and ToLower methods • Replace UCase and LCase functions • If txtInput.Text.ToUpper = “YES”

44. Arrays • VB 6.0 - Arrays can be defined with lower and upper bounds of any whole number. The Option Base statement is used to determine the default lower bound if a range is not specified in the declaration. • VB.NET- To enable interoperability with other languages, all arrays must have a lower bound of zero. This makes the Option Base statement no longer necessary. • Dim a(1 To 10) As String is upgraded to: Dim a(10) As String

45. Array Size • This is one area that was going to change, but did not • When you declare an array, it starts at zero, and the element number you use is the Upper Bound of the array • This means that arrays will always be one larger than the size declared • Dim x(2) As Integer has three elements

46. Arrays Continued • Arrays in VB.NET are classes supporting properties and methods, making them quite flexible. • .Sort • .Reverse • You can sort an array in one line of code!

47. Garbage Collection • The garbage collector periodically checks for unreferenced objects and releases all memory and system resources used by the objects • VB’s garbage collection reclaims object space automatically behind the scenes • For efficiency, VB only runs the garbage collection feature when: • There are objects to recycle • There is a need to recycle them

48. While Loops • VB 6.0 - While statements are ended with a WEND statement. • VB.NET - WEND statements are changed to End While. This improves language consistency and readability. • While End While

49. Parameter Passing • VB 6.0 - Parameters that do not specify either ByVal or ByRef default to ByRef • VB.NET - Parameters that do not specify either ByVal or ByRef default to ByVal. Defaulting to ByVal rather than ByRef eliminates the problem of having a procedure mistakenly modify a variable passed in by the caller.

50. GoSub, On Goto • VB 6.0 - The GoSub line ... Return statement branches to and returns from a subroutine within a procedure. • VB.NET - GoSub...Return is a nonstructured programming construct. Its use makes programs harder to read and understand. Creating separate procedures that you can call may provide a more structured alternative or use case statements.