Type Libraries and ActiveX Objects

You must create a type library for each set of exposed objects. Because VTBL references are bound at compile time, exposed objects that support VTBL binding must be described in a type library.

Type libraries provide these important benefits:

  • Type checking can be performed at compile time. This may help developers of ActiveX clients to write fast, correct code to access objects.

  • You can describe an interface with type information and implement IDispatch::Invoke for the interface using a single call to DispInvoke.

  • Visual Basic applications can create objects with specific interface types, rather than the generic Object type, to take advantage of early binding.

  • ActiveX clients that do not support VTBLs can read and cache DISPIDs at compile time, improving run-time performance.

  • Type browsers can scan the library, allowing others to see the characteristics of objects.

  • The RegisterTypeLib function can be used to register exposed objects in the registration database.

  • The UnRegisterTypeLib function can be used to completely uninstall an application from the system registry.

  • Local server access is improved because Automation uses information from the type library to package the parameters that are passed to an object in another process.

In this section


Creating a Type Library

Demonstrates how to create a type library.

Building a Type Library

Demonstrates how to build a type library.

Registering a Type Library

Demonstrates how to register a type library.

Returning an Error

ActiveX objects typically return rich contextual error information, which includes an error number, a description of the error, and the path of a Help file that supplies more information.