Advanced Visual Basic

1
Advanced Visual Basic

• ActiveX Components

2
Types of ActiveX Components

• ActiveX EXE
• Can be run standalone or as a server. When run
  as a server, runs out of process.
• ActiveX DLL
• Can only run as a server. Runs in process.
• ActiveX OCX
• Must be run from an ActiveX container like a form
  or a web page.

3
Component Communication

• ActiveX components communicate by public
  properties, methods, enums and events.
• To establish ActiveX communication
• Set project reference
• Dim variable as class
• Set variable new class
• Reference variable.(property, method, enum)
• Handle variable_event

4
Exposure

• Private
• A private variable, property, or method is only
  available to the class from which it is called.
• Friend
• A friend property or method is available to any
  classes within the ActiveX component. Variables
  cannot be declared as friend.
• Public
• A public property or method is available to
  whatever object instantiated it.

5
Hierarchy Review

• Application
• ActiveX Component (EXE, DLL, OCX)
• Collections (Optional)
• Class
• Properties
• Methods
• Enums
• Events

6
Marshalling

• Marshalling refers to the cross process
  communication between two components.
• Occurs when an out of process (EXE) component is
  used by another component.
• Marshalling is much slower than in process
  communication.

7
Marshalling Optimized

• Dont pass an object when a property will do
• An object requires much more overhead than a
  property.
• If you do pass an object, do it ByVal
• A one-way communication.
• Use parameters instead of setting properties.
• Causes only one communication to occur.

8
Class Properties

• Instancing
• Can a client application create instances of the
  class?
• If so, how?
• MTS Transaction Mode
• How class reacts when using Microsoft Transaction
  Server
• Only available to DLLs.
• Persistable
• Whether on not object can be saved

9
Project Properties General Tab

• Project Type - Set to ActiveX DLL or ActiveX EXE
  for ActiveX components
• Startup Object
• None - no startup code required
• Sub Main - start using the Sub Main procedure  
• Project Name - Identifies ActiveX component
• Project Description - Appears in the Object
  Browser 
• Unattended execution - Run without user
  interaction - useful on remote systems
• Threading Model - By default, an application has
  a single thread of execution
• One Thread per object - objects are independent
• Thread Pool - fewer objects than threads each
  object has its own thread. Otherwise, objects
  share threads.

10
Project Properties Version Compatibility

• No Compatibility Choose this if making a change
  to a component to sever ties with previous
  component class IDs
• Project Compatibility Choose this during
  testing to assure that when you close a project
  and reopen it, class IDs are maintained
• For all ActiveX project types, Project
  Compatibility is checked by default
• Binary Compatibility Necessary for maintaining
  compatibility among projects that have been
  compiled using your component.

11
Testing and ActiveX Component

• Project group
• This is a good idea when you're testing an
  ActiveX DLL or OCX. This allows you to step
  through the code of your component
• Client Project using ActiveX Start Mode
• You can't use a project group to test an ActiveX
  EXE, you have to run the ActiveX EXE in one copy
  of VB and the client in another copy of VB

12
Testing an ActiveX EXE

• Compile the ActiveX EXE
• Set Project compatibility to the ActiveX EXE
• Set Start Mode of component to ActiveX Component
• Run the ActiveX EXE
• Open the client application in a separate VB
  window
• Be sure to set References (from Project menu) to
  the compiled EXE
• Run the client

13
Compiling the Component

• Choosing Make from the File Menu
• Compiles the component
• Creates a Windows registry entry
• Creates a type library (provides a description of
  the interfaces)
•  
• Every compile creates a set of Globally Unique
  Ids (GUIDs) for all classes and interfaces in the
  component. If Version Compatibility is set,
  GUIDs are not generated

14
Distributing Your Application

• When you distribute an application, there are two
  steps you must go through
• Packaging you must package your application
  files into one or more .cab files that can be
  deployed to the location you choose, and you must
  create setup programs for certain types of
  packages.
• Deployment you must move your packaged
  application to the location users can install it
  from.
• The Package and Deployment Wizard is the easiest
  way to create your application package.