InvokeDISPID

InvokeDISPID is a descriptive term used in COM development to refer to invoking a member of a COM object that supports IDispatch by using its dispatch identifier (DISPID). In automation objects, client code typically first resolves a member name to a DISPID via IDispatch::GetIDsOfNames, then calls IDispatch::Invoke with that DISPID to perform the call. The DISPID identifies the member to invoke; wFlags specify whether the call is a method invocation, a property get, or a property put.

The IDispatch::Invoke function receives the DISPID, locale, flags, arguments packaged in a DISPPARAMS structure, and returns the result in a VARIANT. If the member is not found or invocation fails, COM returns an appropriate HRESULT and optionally EXCEPINFO. Arguments are supplied in reverse order in the pDispParams.rgvarg array; there is an optional named argument array for named parameters.

Use cases include scripting engines and automation clients written in languages that support late binding, where the exact types are not known at compile time. Performance considerations arise from late-bound dispatch and marshaling across COM boundaries. Error handling with DISP_E_* codes and arg errors is an important part of robust InvokeDISPID use.

Note that "InvokeDISPID" is not a separate API function; rather, it is a convention for describing the action of invoking a DISPID via IDispatch::Invoke. See also IDispatch, GetIDsOfNames, DISPID, DISPPARAMS.