OleDoAutoConvert - OLE Programmer's Reference (ole.hlp)

OleDoAutoConvert

Automatically converts an object to a new class if conversion is needed.

HRESULT OleDoAutoConvert(

IStorage * pStg,	//Pointer to storage object to be converted
LPCLSID pClsidNew	//Points to new CLSID of converted object
);

Parameters
pStg

Points to the persistent storage of the object to be converted.

pClsidNew

Points to the new CLSID for the object being converted. If there was no automatic conversion, this may be the same as the original class.

Return Values
S_OK

Indicates no conversion is needed or a conversion was successfully completed.

REGDB_E_KEYMISSING

Indicates cannot read a key from the registration database.

E_OUTOFMEMORY

Indicates the conversion was not successful due to a lack of memory.

E_INVALIDARG

Indicates one or more arguments are invalid.

E_UNEXPECTED

Indicates an unexpected error occurred.

See also the OleGetAutoConvert function for other error return values.

See the IStorage::OpenStorage and IStorage::OpenStream methods for possible errors when accessing storage and stream objects.

See also the IStream interface for other error return values when it is not possible to determine the existing CLSID or when it is not possible to update the storage object with new information.

Comments
This function automatically converts an object if automatic conversion has previously been specified in the registry by the OleSetAutoConvert function. Object conversion means that the object is permanently associated with a new CLSID. Automatic conversion is typically specified by the setup program for a new version of an object application so that objects created by its older versions can be automatically updated.

A container application that supports object conversion should call the OleDoAutoConvert function each time it loads an object. If the container uses the OleLoad helper function, it need not call OleDoAutoConvert explicitly because OleLoad calls it internally.

The OleDoAutoConvert function first determines whether any conversion is required by calling the OleGetAutoConvert function. If no conversion is required, the function returns S_OK. Otherwise, the storage object is modified and converted by activating the new object application. The new object application reads the existing data format but when the object is saved, the new native format for the object application is saved.

If the object to be automatically converted is an OLE 1 object, the ItemName string is stored in a stream called "\1Ole10ItemName." If this stream does not exist, the object's item name is NULL.

The storage object must be in the unloaded state when OleDoAutoConvert is called.