OleRegEnumFormatEtc

Enumerates data formats that an OLE object server has registered in the registration database. An object application or object handler calls this function to obtain an enumeration of those formats. Developers of custom DLL object applications use this function to emulate the behavior of the default object handler.

HRESULT OleRegEnumFormatEtc(

REFCLSID clsid,	//Reference to class identifier
DWORD dwDirection,	//Value specifying data formats
LPENUMFORMATETC * ppenumFormatetc	//Pointer to returned format information
);

Parameters
clsid

Specifies the class whose formats are being requested.

dwDirection

Specifies whether to enumerate formats that can be passed to IDataObject::GetData or formats that can be passed to IDataObject::SetData. Valid values are taken from the enumeration DATADIR.

ppenumFormatetc

Points to where to return the enumeration.

Return Values
S_OK

Indicates the enumerator was returned successfully.

E_OUTOFMEMORY

Indicates there is insufficient memory to complete the operation.

REGDB_E_CLASSNOTREG

Indicates there is no CLSID registered for the class object.

REGDB_E_READREGDB

Indicates there was an error reading the registry.

OLE_E_REGDB_KEY

Indicates the DataFormats/GetSet key is missing from the registry.

Comments
Object applications can ask OLE to enumerate supported data formats in one of two ways. One way is to call OleRegEnumFormatEtc. The other is to return OLE_S_USEREG in response to calls by the default object handler to IDataObject::EnumFormatEtc. OLE_S_USEREG instructs the default handler to call OleRegEnumFormatEtc. Because DLL object applications cannot return OLE_S_USEREG, they must call OleRegEnumFormatEtc rather than delegating the job to the object handler.

The OleRegEnumFormatEtc function and its sibling functions, OleRegGetUserType, OleRegGetMiscStatus, and OleRegEnumVerbs, provide a way for developers of custom DLL object applications to emulate the behavior of OLE's default object handler in getting information about objects from the registry. By using these functions, you avoid the considerable work of writing your own, and the pitfalls inherent in working directly in the registry. In addition, you get future enhancements and optimizations of these functions without having to code them yourself.