What’s Happened to Visual Basic?

1. What’s Happened to Visual Basic? Everything is an object now.

2. Overview • Describe the strategies behind VB.NET and Visual Studio.NET • Discuss changes to the developer interface (IDE) • Identify significant VB.NET language changes • Introduce C# • Introduce ADO.NET • Using VB.NET as a teaching language

3. VB.NET Strategies • Reinventing Internet development • and desktop development along the way • Technology ‘marries’ Windows and the Internet • Visual Studio.NET • Windows.NET (code named Whistler) • The conflict • Windows is a cash cow so preserving the PC is important • .NET generates no revenue today but if successful will turn Microsoft into an Internet powerhouse • Remember the transition from DOS to Windows

4. VB.NET - Introduction • The new name for Visual Basic • In summary, it’s a new language and a new development environment • Form and Code windows have been overhauled • Module and program structure is new • Supports object-oriented features including overloading, inheritance, etc. • Supports an integrated Web development environment

5. What is in Visual Studio.NET? • Common IDE shared by all Visual Studio.NET applications • C++, C#, Visual FoxPro, VB.NET • J++ is not part of Visual Studio • Visual InterDev appears to be obsolete • Common Language Runtime (CLR) exposes objects instead of COM • COM supported through wrapper procedures for backward compatibility • Common Type System (CTS) standardizes data types between all Visual Studio.NET languages • ADO.NET replaces ADO • ASP.NET replaces ASP

6. Converting VB6 Programs • Conversion Wizard activated by opening a .vbp file • Uses compatibility libraries to migrate COM objects • So it is not writing the best managed code • Uses Microsoft.VisualBasic.Compatibility.VB6 namespace • Late Binding causes problems • Control instances convert well • Those that don’t convert are turned into labels • First iteration of tool • Did not ship with the PDC Preview edition • Will likely undergo further development

7. IDE Change Summary • New default development environment • Modules displayed in tabbed dialogs similar to previous Visual Studio editions • MDI mode is supported but SDI mode seems to be obsolete • SDI mode appeared in PDC preview but not in Beta 1 • Enhanced window management features • Docking and auto-hide • Enhanced debugging windows

8. Window Types • Document windows • Appear on individual tabs • Multiple tabbed lists supported • Each tab corresponds to a module file • Tool windows • Dockable along any edge • Auto-hide allows windows to be hidden along any window edge to maximize screen real estate • Some tool windows can appear as document windows • Solution Explorer, Help Windows • Windows can float on desktop

9. VB.NET - IDE Document windows Auto-hide Docked tool windows

10. Projects are now Solutions • Solution Explorer replaces the Project Explorer • Conceptually the same window though • Project groups (.vbg files) no longer exist • Solution file replaces project group • Projects contained by solution • Project contains references to namespaces • Solution and projects are organized into multiple directories

11. Solution Explorer References to namespaces Solutions contain multiple directories

12. The Toolbox and Controls • VB.NET controls are no longer COM controls • Controls based on .NET assemblies • Control names and interfaces have changed • Button control replaces Command Button • Shape and Line not supported • Functionality replaced by System.Drawing namespace • Six separate controls replace the CommonDialog control • GroupBox replaces frame • Property names have changed too • Text property replaces Caption in most cases • Default properties no longer supported • Control arrays are not supported by .NET

13. The Toolbox Auto-hide enabled Tabs group controls based on function Multiple clipboards supported

14. The WinForm Designer • Forms divided into WinForms and WebForms • WinForm designer works like the Form window • Process of creating, moving, resizing a control instance is the same as previous editions • Form window contains a tray to display invisible control instances • ImageList, OpenFileDialog, etc. • WinForm designer creates exposed code to: • Import namespaces • Instantiate the form • Create control instances

15. Debugging Windows • Locals and Watch windows operate similar to VB6 • Autos window shows variables in current and previous statement • This window examines current class instance (Me keyword) • Modules window lists modules (DLLs) used by a program • CallStack window shows procedure call sequence • Output window shows compilation results • VB.NET performs real compilation – All syntax errors discovered at compile time • Breakpoints window lists current breakpoints • Breakpoints now persistent between invocations

16. Command Window • Command window replaces Immediate window • Command mode used to execute Visual Studio commands bypassing menu system • Useful to create command macros • Display the Open File dialog File.OpenFile • Immediate window used for debugging • Similar to VB6 • Note Debug class has new properties and methods

17. Menus • Menu implementation has changed • Use MainMenu control in Toolbox to create menu • Menu creation is now ‘in place’ • Create menus directly on the WinForm designer • MainMenu class defines menu • MenuItem class defines subordinate menu items • MenuItems can contain subordinate menu items to define sub menus • Menu integration implemented differently in MDI applications

18. Anatomy ofa WinForm In-place menu editor New checked list box and NumericUpDown controls Controls support images and text alignment Invisible controls appear in tray

19. The .NET Framework • Classes are exposed through assemblies • Compare an assembly to an .ocx file • Assemblies contain one or more namespaces • Namespaces are similar to the classes exposed by an .ocx file • Access to COM provided through wrapper procedures supplied by compatibility namespaces • Microsoft.VisualBasic.Compatibility.VB6

20. Common Language Runtime • All Visual Studio.NET languages share the same run-time • CLR performs object creation and destruction • Garbage collector destroys objects • Runs periodically as a background thread • Object destruction no longer occurs when reference counter becomes zero • Conceptually implemented similar to the Java virtual machine • We could be running .NET under Sun Solaris • All code compiled to standard Intermediate Language (IL) in .NET

21. Common Type System • All .NET languages use the Common Type System • Required for language interoperability • Changes to VB data types • New Char type contains single character • Date data type is no longer a double • Long Integer is 64 bits • Integer is 32 bits • New Short data type is 16 bits • Variant not supported • Generic late bound Object type still exists • All data types are represented as classes

22. Code Modules • Code Editor is the new term for the Code window • New features • Statements automatically indented • Procedures can be expanded or collapsed • #Region / #End Region “preprocessor” directives allow statement and procedure grouping • Expand or collapse large code blocks • Techniques to select event procedures has changed • Syntax errors appear in Task window • VB.NET performs full syntax check when compiled • No need to correct 1 error at a time

23. CodeEditor Region / procedures can be expanded or collapsed Task window displays errors

24. Language Changes – Overview • New type conversion rules • Arrays implemented differently • They are now classes supporting methods • Structured error handling • New OOP features • Static classes replace many intrinsic functions • Inheritance – Implementation and Interface • Parameterized constructors • Overloading • Methods, properties, constructors

25. Strict Type Checking • New Option Strict statement prohibits: • Implicit numeric to string type conversion • Implicit type conversion to more restrictive types • Long to Integer • Double to Single • Late binding of object variables • Great for structured programming purists • Even better for teaching data types and type conversion

26. Namespaces – Getting to Objects • Access to all classes is through a namespace containing one or more classes • Namespaces are hierarchical. Namespaces may contain other namespaces • Imports statement provides a module with a namespace reference Imports SystemImports System.ComponentModelImports System.DrawingImports System.WinForms

27. Type Conversion – The Old and the New • Functions CInt, CLng, CSng, CDbl etc. still supported but: • Variables are really classes too • Remember everything is an object • We say that the Integer and Long data types are represented as class structures provided by the System namespace • Thus, variables support type conversion methods such as Format and ToString

28. Type Conversion - Example Dim pintX As Integer = 33344 Dim plngX As Long plngX = CLng(pintX) plngX = pintX.ToInt64 Note automatic initialization Convert Integer to Long with intrinsic Function Convert Integer to Long using static method

29. Array Upgrades • All arrays are 0 based • Option Base statement no longer supported • Fixed size arrays are obsolete – All arrays are dynamic • Arrays are classes too so we call methods to: • Perform a binary search • Copy arrays or parts of an array • Sort arrays

30. Sorting Made Easy Dim A1() As Integer = {134,224,18,955,3,994} System.Array.Sort(A1) Declare a dynamic array and initialize it using c-like syntax Sort the array by calling the Sort method pertaining to the Array class

31. Static Classes Replace Intrinsic Functions • Many intrinsic functions are replaced by static classes • Math class contains mathematical functions • String class contains string functions • And many more • Get absolute value using Math class pintFoo = System.Math.Abs(-442)

32. Structures • Structures replace user-defined types • Structures may contain methods • Similar to classes • Declaration syntax has changed Public Structure Customer Public Name As String Public Address As String End Structure

33. Assigning Object References – The Set Statement is Gone • VB6 required the Set statement to assign object references because of default properties • Default properties no longer supported • Set statement obsolete Dim t As New Thing Dim tRef As Thing tRef = t

34. Structured Error Handling • Try… Catch… Finally… statements provide a structured error handling mechanism • Try block executes code that may cause a run-time error • Catch block provides error trap • Based on exceptions • Multiple Catch blocks trap different exceptions • Finally block always executes • Use for housekeeping • Replaces On Error Resume syntax • On Error still supported for backward compatibility

35. Error Handler – Example Dim srdCurrent As System.IO.StreamReader Dim pstrLine As String, pstrFile As String ofdCommon.showdialog() ‘ Display OpenFileDialog Try srdCurrent = New System.IO.StreamReader(ofdCommon.Filename) mstrLine = srdcurrent.ReadLine() Do Until mstrline = Nothing mstrLine = srdCurrent.Readline() Loop srdCurrent.Close() pstrMessage = “File Opened.” Catch excCurrent As Exception pstrMessage = “Cannot open file.” Finally MsgBox(pstrMessage,,”Module Status”) End Try

36. Drawing – Graphical Methods • Form methods obsolete – Replaced by System.Drawing namespace • Methods closely correspond to the GDI • Provides functionality previously available only through API calls • Use pens to draw lines / arcs, and outline rectangles • Use brushes to fill rectangles • Draw graphical shapes with Graphics class

37. Drawing a Rectangle • First define a color • Apply the color to a brush • Fill rectangle using brush and color Dim colCurrent As Color = Color.FromARGB(255,255,255,255)Dim sbCurrent As New SolidBrush(colCurrent) Dim recCurrent As New Rectangle(1,1,72,72) e.Graphics.FillRectangle(sbCurrent,recCurrent)

38. Drawing a Line • Define a color and apply it to a pen • Draw a line using a pen Dim penLine As New Pen = Pen(Color.FromARGB(1,1,1)) e.Graphics.DrawLine(penLine,1,1,100,100)

39. VB.NET is an OOP Language • VB.NET is formally an OOP language • Parameterized constructors • Supply arguments when creating an object from underlying class • Inheritance (interface and implementation) • Overloading • Multiple methods can have the same name and varying arguments • Procedures, properties, methods, and constructors can be overloaded

40. Parameterized Constructors • Arguments allowed when constructing objects from a class • Parameters may be overloaded • Create a StopLight using 3 different parameterized constructors Dim LightNorth, LightSouth, LightEast As StopLight LightNorth = New StopLight() LightSouth = New StopLight(StopLight.eLight.Green) LightEast = New StopLight(StopLight.eLight.Green,2500,500,3000)

41. Overloading • Constructors, methods, and properties may be overloaded • Methods of the same name support a variable number of arguments • Arguments may have different types • CLR detects which method to call based number and data type of arguments

42. Overloaded Constructors • New procedure is called by CLR when a class instance is initialized • Replaces Class_Initialize event • May have arguments • Procedure may be overloaded • Overloads keyword marks an overloaded procedure

43. Overloaded Constructors – Example Public Overloads Sub New() ‘ statements End Sub Public Overloads Sub New(byVal pLight as eLight) ‘ statements End Sub

44. Overloaded Help Sort method is overloaded

45. Inheritance • VB6 supported interface inheritance through abstract classes • The implementation was poor • Implementation inheritance was not supported • We could not derive a class from another class • VB.NET supports both implementation and interface inheritance • Inherits keyword used to create a derived class from a base class • Overrides keyword is used to override a method defined in the inherited class

46. Inheritance – Uses • Every form inherits from the System.WinForms namespaceInherits System.WinForms.Form • Forms are classes • Create a form designed as a template • Have developers inherit the template into their programs • Develop realistic object models from VB.NET classes

47. ADO+ • Next generation of ADO • XML used as transmission protocol • Disconnected recordset superceded by new DataSet class • In memory copy of data • May contain multiple tables and queries • All of the controls and development tools have changed considerably • Much more complex

48. C# (pronounced c-sharp) • New development language • Shares syntactical elements of Visual C++ and Visual Basic • The best of both worlds? • All languages share the same run-time so that all share the same namespaces • Microsoft hopes to replace Java?

49. Comparing VB.NET and C#

50. Release Schedule • 2 to 3 betas • Release candidate 4th quarter 2001