Visual Basic.NET

Taking the Most Successful Language One Step Further

Objectives

Introduction to Microsoft Visual Basic.NET New concepts Changes

Integration into .NET

Tools

Contents

Section 1: Overview

Section 2: Language Features

Section 3: Integration into .NET

Section 4: Putting It All Together

Summary

Section 1: Overview

Make the language even easier to use ...at least easier to learn

Get rid of some design flaws

Add full set of object-oriented programming features

Make it a first-class citizen of the .NET world

...but don't reinvent the language

First-Class Object Orientation

Concept of classes and interfaces Inheritance Overloading Shared members Constructors and initializers

Sub New()

anObject = New Class(“Data”, data)

Object-oriented event system

Inheritance Concepts

Concept of Reuse Composition (Has-A)

MyForm Has-A Control

Inheritance (Is-A) MyForm Is-A EntryForm

Building Type Hierarchies

Versioning

Polymorphism

MyForm Control

Form

EntryForm

MyForm

MyNewForm

Section 2: Language Features

Type System

Classes and Inheritance

Exception Handling

Event Concept

Changes

Type System

Uses the .NET common type system No need for marshalling between languages

Every type is either a value or a reference type Value types:

Primitives, enumerations, structures

Reference Types: Classes, modules, interfaces, arrays, delegates, and strings

Object can contain both Everything implicitly inherits from System.Object

Primitive Types Integral Types

Byte (8 bits), Short (16 bits) Integer (32 bits), Long (64 bits)

Floating-Point Types Single (4 bytes), Double (8 bytes)

Exact Numeric Type Decimal (28 digits) (replaces Currency)

Boolean, Date, Char

String (Reference Type!)

Signed bytes and unsigned integers not supported

Enumerations

Symbolic name for a set of values

Strongly typed

Based on integral type Byte, Short, Integer, or Long Integer is default

Example: Enum Color As Byteredyellowgreen

End Enum

Arrays

Built on .NET System.Array class

Defined with type and shape

Declaration only syntax

Lower bound index is always zero

Fixed size no longer supported

Rank cannot be changed

Dim anArray() As IntegerReDim anArray(10)

Dim OneDimension(10) As IntegerDim TwoDimensions(20,intVal) As Integer

Interfaces

Declare semantic contracts between parties Enable component orientation

Define structure and semantics for specific purpose

Abstract definitions of methods and properties

Support (multiple) inheritance

Example: Interface IPersonAge

Property YearOfBirth() As Integer

Function GetAgeToday() As Integer

End Interface

Classes Concept for objects: data and code

Classes contain members: Data members: variables, constants Properties: values accessed through get/set

methods Methods: functionality for object or class

Subs and Functions

Specials: events, delegates, constructor

Concept of Overloading Method Overloads another

With same name, but different parameters

Accessibility

Each member can have its own accessibility Private

Restricted to context of declaration

Protected (class members only) Additional access by derived classes

Friend Access from same assembly

Protected Friend Union of Protected and Friend access

Public No restrictions

Properties Not a storage location—can be computed

Usage like data members

Can be ReadOnly or WriteOnly

Public Class Sample Private m_val as Integer Public Property val() as Integer Get return m_val End Get Set m_val = value End Set End PropertyEnd Class

intVal = Sample.val

Sample Class DefinitionPublic Class CustomerImplements ICustomer

Private CustomerNo As String

Public Property Customer() As String Get Return CustomerNo End Get Set CustomerNo = Customer End SetEnd Property

Public Overloads Sub New()End Sub

Public Overloads Sub New(ByVal par as Integer) MyBase.New(par)End Sub

Public Sub DoAny(ByVal c as Char) Implements ICustomer.DoAnyEnd Sub

End Class

Inheritance 1/2

Single base class, but multiple base interfaces

Abstract base classes

Non-inheritable classes

Public Class DerivedClassInherits BaseClassImplements IBase1, IBase2...

End Class

Public MustInherit Class AbstractBase ...End Class

Public NotInheritable Class FinalClass...End Class

Inheritance 2/2

Overrides Method overrides another with same signature

NotOverridable (default) Cannot be overridden

MustOverride Must be overridden – empty method body

Qualified access MyClass, MyBase

Structures User-defined types—replace Type

Lightweight “Classes“ Consists of the same members Is value types, Classes are reference types Can implement Interfaces Can not be inherited

Public Structure CustomerImplements ICustomer

Public CustomerNo, Name As String

Public Sub New()End Sub

Public Sub Do(ByVal c as Char) Implements ICustomer.DoEnd Sub

End Structure

Exception Handling

Exceptions are not necessarily errors

Two styles: structured (SEH) and unstructured (UEH)

Only one style allowed in a method

UEH supported for backward compatibility On Error, Resume, Error Microsoft.VisualBasic.Information.Err

Structured Exception Handling Exceptions are system concepts

Propagated between components

Syntactical form of handling:

Can define custom exceptions Derived from System.Exception

Exceptions can be user-defined and thrown explicitly Throw

Try <something risky>Catch e As Exception <recover from the exception>Finally <execute this regardless>End Try

Delegates Object-oriented function pointers

Can point to a specific method of a specific instance

Delegate Function CmpFunc(x As Integer, y As Integer) As Boolean

Public Function Cmp(x As Integer, y As Integer) As Boolean... (This function implemented in some class)End Function

Sub Sort(Sort As CmpFunc, ByRef IntArray() As Integer) ... If Sort.Invoke(IntArray(i), Value) Then ... Exchange values End If ...End Sub

Call Sort( new CmpFunc( AddressOf aObj.Cmp), AnArray)

Events

Traditional WithEvents style still supported

New event system based on .NET Framework Implemented on top of delegates

Multicast events

Dynamic hookup of method as handler

AddHandler, RemoveHandler

Many events can be routed to same method

Private WithEvents mW As Widget

Public Sub mW_MouseHover(...) Handles mW.MouseHover

Simpler, More Consistent

Boolean operators And, Or, Xor, and Not are still bitwise AndAlso and OrElse added for short-circuiting

More obvious declarations Visual Basic 6: Dim i,j as Integer

i is Variant, j is Integer Visual Basic.NET: Dim i,j as Integer

i and j are Integer

Variables declared in a block have block scope

No implicit object creation—must use New

More Robust

Strict type checking

Implicit and explicit type conversions

Option Strict

Option Explicit

Optional parameters must have default values

Sub Calculate(Optional ByVal param As Boolean = False)

Dim Base as CBaseDim Derived as CDerived = new CDerived()

Base = Derived

Better Performance

Supports free threading More responsiveness

Short-circuit evaluation X = A AndAlso B AndAlso (C OrElse D)

Reference assignment for arrays

Some Other Changes

Parentheses around nonempty parameter lists Always required for function and procedure calls

Default parameter passing method is now ByVal

Properties as reference parameters Changes are now reflected back

Gosub/Return no longer supported

Default data types no longer supported

Arithmetic operator shortcuts: x += 7

Late binding

Deterministic Finalization

An object used to be destroyed automatically Just at the moment it is no longer needed

No longer available with Visual Basic.NET: No automatic reference counting behind the scenes Objects are destroyed at garbage collector’s choice Resources may stay locked virtually forever

One possible solution: Provide your own reference counting and disposal scheme

Make your objects stateless

Section 3: Integration into .NET

Common Language Runtime

Concepts of Namespaces, Assemblies, Modules

Free Threading

Reflection

Attributes

Windows Forms

Tools

The Common Language Runtime

Access to .NET platform services

Cross-language interoperation That includes inheritance

Interoperation w/ COM and Platform Invocation Services COM-Interop PInvoke Calling unmanaged code has its implications

Namespaces Organizational concept

May and should be nested System.Reflection MyLib.Helpers.Controls.Inputs

Multiple namespaces declared in program

Namespaces can span multiple programs

Importing namespaces Allows unqualified access to types Placed at file or project level

Global namespace without a name Globally declared members have program scope

Namespace MyLib

...

End Namespace

Assemblies

Result of compiling is still a .dll or .exe file Single-file or multiple-file assembly

File contains metadata (manifest) Description of the assembly itself Description of implemented types External references Version information Enforce security And more ...

Modules

Smallest unit that can be compiled

Contains one or more classes or interfaces Sub Main() usually has module scope

More than one module can share an assembly which is an multifile assembly then

Example: Imports System Public Module MainMod Sub Main() Console.WriteLine("Hello World!") End Sub End Module

Free Threading

Run multiple tasks independently Objects can be shared by threads

Use AddressOf operator on Sub to declare

Sub cannot have arguments or return value

Synchronization needed

Dim myThread As New Threading.thread(AddressOf MySub)

myThread.Start()

myThread.Join()

Threading Sample

Dim Writer As Thread = new Thread(AddressOf AnObj.ThreadSub)

Dim Reader As Thread = new Thread(AddressOf AnObj.ThreadSub)

...

Writer.Start()

Reader.Start()

Writer.Join()

Reader.Join()

...

Public Sub ThreadSub

Monitor.Enter(Me) 'Enter Synchronization block

...

Monitor.Exit(Me)

End Sub

Reflection

Mechanism for obtaining run-time information Assemblies Types: classes, interfaces, methods

Provides explicit late-bound method invocation

May even construct types at run time System.Reflection.Emit

Attributes Additional declarative information on program item

May define custom attribute classes

Can be retrieved at run time

Enhance program functionality Giving hints to the system runtime

Use as meta elements

Public Class PersonFirstName Inherits AttributeEnd Class

<PersonFirstName()> Dim Vorname As String<PersonFirstName()> Dim NamaDepan As String

<WebMethod()> Public Function Hello As String ...

Windows® Forms

New forms library based on .NET Framework

Can be used for desktop applications

Local user interface for three-tier applications

Windows Client Web Service

DatabaseForm1.vb Business Object GetOrder

Dataset

orders.xsdDataset

orders.xsdDataset Command

orderCommand

HTTP

XML

OLE DB

Command-Line Compiler

Compiles Visual Basic source into MSIL

Can have a multitude of options

Can be called from arbitrary environment

Uses fewer system resources than Visual Studio

Can be used with nmake Useful for multi-language projects

Vbc /target:exe /out:myprogram.exe *.vb

Visual Studio.NET

Built around the .NET Framework SDK

Improved integration and functionality Multiple-language projects One integrated IDE for all languages and tasks Integrated tools: Visual Modeler, database management Perfect help integration: Dynamic Help, IntelliSense®

Highest productivity for all: Rapid application development Large-scale projects

From Visual Basic 6 to Visual Basic.NET

Visual Basic.NET is a true successor of Visual Basic 6 ...but some things make a difference

Compatibility classes help with the transition Microsoft.VisualBasic imported by default Classes that deliver the functionality of...

Collections

Date/time functions

More

Prepare for porting!

Visual Basic Upgrade Wizard

Applies changes automatically

Generates solution Type conversions

Variant to Object

Integer to Short, Long to Integer

Type to Structure

Currency to Decimal

Zero-bound arrays .NET Windows Forms replace Visual Basic 6 Forms

Recommendations for upgrading

Section 4: Putting It All Together

Sample Walkthrough Exploring Visual Basic.NET Features in Duwamish Books

Demo: Duwamish Books

Enterprise Sample application

"Best practice" multiple-tier design

Included with Visual Studio.NET

Great start to learn about Visual Basic.NET ASP.NET ADO.NET

Summary

Major touchup to take advantage of the .NET Framework

Modernized and consistent language

Legacy features finally dropped

Your Visual Basic.NET code can be reused

Supported migration path

Questions?

Duwamish Books

A Sample Application for Microsoft .NET

Installing the Sample 1/2

Install the "Enterprise Samples" with Visual Studio.NET

Location of the Visual Basic Version Directory .\EnterpriseSamples\DuwamishOnline VB

Installation Tasks Check the prerequisites

Microsoft Windows 2000 Server; Microsoft SQL Server™ 2000 with English Query optional and supported

Read the Readme.htm

Run Installer Duwamish.msi (double-click it)

Installing the Sample 2/2

The installation wizard will guide you

Defaults should be OK for almost everybody.

Setup will install database, Web site, and code

After installation is complete: File/Open Solution with the Duwamish.sln file Can build the sample with Build/Build Solution

User / Browser

IIS

Duwamish Architecture Overview

DataAccess

Database

Com

mon.D

ata

BusinessRules

BusinessFacade

System

Fram

ework

Web

ASP.NET

ADO.NET

Common Components Duwamish7.Common

Contains systems configuration options Contains common data definitions (classes)

subnamespace Duwamish.Common.Data

"Internal" data representation for Book, Category, Customer, OrderData

Duwamish7.SystemFramework Diagnostics utilities Pre and post condition checking classes Dynamic configuration In short:

Everything that's pure tech and not business code

Duwamish7.DataAccess

Contains all database-related code

Uses ADO.NET architecture Using SQL Server managed provider Shows DataSet, DataSetCommand usage

Optimized for performance by using stored procs

Duwamish7.BusinessRules

Implements all business rules Validation of business objects (for examle,

Customer EMail) Updating business objects Calculations (Shipping Cost, Taxes)

All data access performed through DataAccess

Duwamish7.BusinessFacade

Implements logical business subsystems CustomerSystem: Profile management OrderSystem: Order management ProductSystem: Catalog management

Reads data through DataAccess

Data validated and updated using BusinessRules

BusinessFacade encapsulates all business-related functionality

Duwamish7.Web

Implements the user interface for Web access

Uses ASP.NET architecture Employs Web Forms model Uses code behind forms Manages state Uses custom Web controls

All functionality accessed through BusinessFacade

Shop at Duwamish Online.NET

Demo: Duwamish in Action

Exploring Duwamish VB

Exploring Visual Basic.NET Features in Duwamish

Extending Duwamish VB

Extending Duwamish VB

Legal Notices

Unpublished work. 2001 Microsoft Corporation. All rights reserved.

Microsoft, IntelliSense, Visual Basic, Visual Studio, and Windows are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries.

The names of actual companies and products mentioned herein may be the trademarks of their respective owners.