Описание тега idispatch

IDispatch Interface

Exposes objects, methods and properties to programming tools and other applications that support Automation. COM components implement the IDispatch interface to enable access by Automation clients, such as Visual Basic.

The IDispatch interface was initially designed to support Automation. It provides a late-binding mechanism to access and retrieve information about an object's methods and properties. Previously, server developers had to implement both the IDispatch and IAccessible interfaces for their accessible objects; that is, they had to provide a dual interface. With Microsoft Active Accessibility 2.0, servers can return E_NOTIMPL from IDispatch methods and Microsoft Active Accessibility will implement the IAccessible interface for them.

http://msdn.microsoft.com/en-us/library/windows/desktop/ms221608%28v=vs.85%29.aspx