This article was previously published under Q221792
After changing the type library version in the .idl file, any method you call in an ATL COM object returns an error of 0x8002801D (TYPE_E_LIBNOTREGISTERED or "Library not registered").
For dual interfaces, the ATL Object Wizard generates code that derives your COM class from IDispatchImpl. IDispatchImpl's fourth and fifth arguments are default arguments that map to the major and minor versions of the type library. These default to version 1.0. ATL uses this version to call LoadRegTypeLib(), which fails with TYPE_E_LIBNOTREGISTERED if the version in the type library doesn't match.
Add the appropriate version number to the template arguments for IDispatchImpl and IProvideClassInfo2Impl, if you are deriving from this class. For example, to set the type library version number to 2.5, your class declaration might resemble the following.
class ATL_NO_VTABLE CMyControl : public IDispatchImpl<IMyControl, &IID_IMyControl, &LIBID_MyControlLib, 2, 5>, public IProvideClassInfo2Impl<&CLSID_MyControl, NULL, &LIBID_MyControlLib, 2, 5>...
If your class derives from CStockPropImpl instead of IDispatchImpl, you need to set the type library version number via member variables, because CStockPropImpl derives from IDispatchImpl but it doesn't provide any template arguments for setting the version number. The major and minor version numbers are actually stored in CComTypeInfoHolder::m_wMajor and CComTypeInfoHolder::m_wMinor. IDispatchImpl contains a CComTypeInfoHolder member called _tih. You can set the version number in your class constructor.