Hello again! :(
I'm trying to implement asynchronous DnD (and Copy/Paste) in a custom NSE:
despite the lack of documentation, I found that i need my DataObject
implement the optional interface IAsyncOperation. I want to always use
asynchronous operations, so I added the following lines to my DataObject
class (I use ATL):

class ATL_NO_VTABLE PPDataObject :
    public CComObjectRootEx<CComSingleThreadModel>, public IDataObject, public
IAsyncOperation{
....
BEGIN_COM_MAP(PPDataObject)
   COM_INTERFACE_ENTRY(IDataObject)
    COM_INTERFACE_ENTRY(IAsyncOperation)
END_COM_MAP()
...

    STDMETHOD(EndOperation)(HRESULT hResult, IBindCtx* pbcReserved, DWORD
dwEffects){
        return S_OK;
    }
    STDMETHOD(GetAsyncMode)(BOOL* pfIsOpAsync){
        return VARIANT_TRUE;
    }
    STDMETHOD(InOperation)(BOOL *pfInAsyncOp){
        *pfInAsyncOp=TRUE;
        return S_OK;
    }
    STDMETHOD(SetAsyncMode)(BOOL fDoOpAsync){
        return S_OK;
    }
    STDMETHOD(StartOperation)(IBindCtx *pbcReserved){
        return S_OK;
    }
...
}

and I call the DataObject as:

CComObject<PPDataObject>* pDataObject;
    //CComObject<>* pAsyncOp;
    hr= CComObject<PPDataObject>::CreateInstance(&pDataObject) ;
    pDataObject->AddRef();
....
hr = ::DoDragDrop( pDataObject, pDropSource, DROPEFFECT_MOVE, &dwEffect);
        pDropSource->Release();
...

The result is that the operation doesn't occur asynchronously (for big files
doesn't occur at all). I read some opinions which stated that implementing
IAsyncOperation doesn't make Explorer use asynchronous transfers, rather
allows it to... But Explorer always uses asynchronous transfers on my
machine, so I can't understand why I can't force it to even in my NSE!
I need to transer big files, passing first through the network, so a lot of
time can be involved in the process and a synchronous scenario doesn't apply:
Please, can anyone tell me what I'm doing wrong? Wrong interface, wrong
implementation, wrong calls, wrong strategy... ???
Thanks in advance for your help!