VB'NET Applying Objects

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VB.NET Applying Objects

• Richard Vantrease

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Introduction

• Using VB.NET to create application objects
  through polymorphism and inheritance.

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Agenda

• Encapsulation
• Polymorphism
• Inheritance

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Encapsulation

• Separating interface from implementation.
• Creating a black box so that developers do not
  know or care about the implementation, just the
  interface.

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Polymorphism

• Late Binding
• Multiple Interfaces
• .NET Reflection
• .NET Reflection Multiple Interfaces
• Polymorphism with Inheritance

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Late Binding

• Object variable is declared without a specific
  type, just uses Object type.
• Cannot be used with Option Strict. Option must
  be turned off in the module file.
• Called method must have same method signature.
• Slower than early binding.
• Errors might be missed until run-time.

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Multiple Interfaces

• Object variable is declared with using a specific
  type.
• Known as strongly typed.
• Interface is known by compiler which helps the
  IDE catch errors sooner.
• Faster than late binding.
• Use with caution and document well as it may
  cause confusion.

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.NET Reflection

• Interrogates .NET external assembly at run-time
  to determine its classes and interfaces.
• Automatically used by Late Binding technique.
• Similar to Late Binding in that interface is not
  really available until compile time.

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.Net Reflection Multiple Interfaces

• Adds strong typing to .NET Reflection.
• Allows the interface to be known even if the
  external assembly is not.

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Polymorphism with Inheritance

• Another form of polymorphism.
• Child class provides expected method signature.

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Inheritance

• Base class is created to define the common
  interface and functionality.
• Child class inherits part of its interface and
  functionality and then extends it to meet the
  needs of its object.
• It is possible to use multiple inheritance where
  a child class inherits from more than one base
  class.

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Framework

• Base classes that are not specific to any
  application, but provide base/common
  functionality only.

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Summary

• While powerful Polymorphism and Inheritance must
  be used carefully and with caution. Can cause
  confusion, or might limit later development.