IDispatchbased

IDispatchbased refers to COM objects or components that expose their automation interface primarily through the IDispatch interface rather than a fixed vtable. In COM, IDispatch provides late binding capabilities that allow scripting languages and other dynamic clients to discover and invoke methods or access properties at runtime. A typical IDispatch-based automation server also provides type information through a type library (.tlb) to make its interface discoverable, though it is not strictly required.

The essential IDispatch methods are GetTypeInfoCount, GetTypeInfo, GetIDsOfNames, and Invoke. Clients call GetIDsOfNames to map a method or property name to a DISP ID, then use Invoke with the DISPID to call the member or to get or set a property. Because calls are resolved at runtime, IDispatch-based interfaces support scripting languages such as VBScript, JScript, and others for automation tasks like controlling Office applications.

IDispatch-based components are common in legacy automation servers and in environments where language interoperability is important. They are often contrasted with early-binding, vtable-only interfaces, or with dual interfaces that expose both IDispatch and vtable bindings. The latter offer fast native calls and still allow scripting through IDispatch.

Developers should consider performance implications, type information availability, and security when implementing or consuming IDispatch-based automation. Modern COM practices favor dual interfaces or type libraries to balance discoverability with performance, but IDispatch-based automation remains widely used for broad scripting support and cross-language interoperability.