EOM Stands for Extensibility Object Model. You might ask what is extensibility? Extensibility is the capability to extend, stretch, the functionality of different development tools, specifically, Microsoft Integrated development environment (IDE). The IDE provides you with a programming interface known as the extensibility object model, a set of powerful interfaces for customizing the environment. It allows you to hook into the IDE to create extensions known as Add-Ins. A good system is the one which can be extended without jeopardizing the primary functionality of the system.

To implement extensibility features, VB offers the powerful Extensibility Object Model. Through EOM, many core objects in VB itself are available to you at no extra charge. EOM is not that easy to learn, this article will provide you only the basics of Add-in creation, you will have to delve into this vast field yourself to explore the wonders you can do using the EOM.

EOM consists of six loosely couple packages of objects with methods that implement key services of the VB development model. These are:

• Core Objects
  
• Form Manipulation
  
• Event Response
  
• Add-In Management
  
• Project and Component Manipulation
  
• Code Manipulation

Core Objects

This package is the main package used in the creation of Add-Ins. It has the following objects:

• The root object
  
• The IDTExtensibility Interface object
  
• The Visual Basic instance variable

The Root Object

VBE is the root object in Visual Basic. The VBE object is the base object for every extensibility object and collection in Visual Basic. Each object and collection owns a reference to the VBE property. The collections owned by the VBE object include the following:

• VBProjects
  
• Windows
  
• CodePanes
  
• CommandBars