OleRegEnumFormatEtc function (ole2.h)

Article
10/13/2021

Creates an enumeration object that can be used to enumerate data formats that an OLE object server has registered in the system registry. An object application or object handler calls this function when it must enumerate those formats. Developers of custom DLL object applications use this function to emulate the behavior of the default object handler.

Syntax

HRESULT OleRegEnumFormatEtc(
  [in]  REFCLSID        clsid,
  [in]  DWORD           dwDirection,
  [out] LPENUMFORMATETC *ppenum
);

Parameters

[in] clsid

CLSID of the class whose formats are being requested.

[in] dwDirection

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

[out] ppenum

Address of IEnumFORMATETC pointer variable that receives the interface pointer to the enumeration object.

Return value

This function returns S_OK on success. Other possible values include the following.

Return code	Description
E_OUTOFMEMORY	Insufficient memory for the operation.
REGDB_E_CLASSNOTREG	There is no CLSID registered for the class object.
REGDB_E_READREGDB	There was an error reading the registry.
OLE_E_REGDB_KEY	The DataFormats/GetSet key is missing from the registry.

Remarks

Object applications can ask OLE to create an enumeration object for FORMATETC structures 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. With the supplied IEnumFORMATETC pointer to the object, you can call the standard enumeration object methods to do the enumeration.

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.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	ole2.h
Library	Ole32.lib
DLL	Ole32.dll