IStorage::SetClass

Assigns the specified CLSID to this storage object.

HRESULT SetClass(

REFCLSID clsid	//Class identifier to be assigned to the storage object
);

Parameter
clsid

[in]The class identifier that is to be associated with the storage object.

Return Values
S_OK

The CLSID was successfully assigned.

STG_E_ACCESSDENIED

The caller does not have sufficient permissions for assigning a class identifier to the storage object.

STG_E_MEDIUMFULL

Not enough space was left on device to complete the operation.

STG_E_REVERTED

The object has been invalidated by a revert operation above it in the transaction tree.

Comments
When first created, a storage object has an associated CLSID of CLSID_NULL. You call this method to assign a class identifier to the storage object.

You can retrieve the current CLSID of a storage object with the IStorage::Stat method.