DragAcceptFiles

int nFileCount = DragQueryFile(hDropInfo, 0xFFFFFFFF, NULL, 0);

    CString strFileName;
    int nFileNameLen = 0;

    if (nFileCount < 2)
    {
        nFileNameLen = DragQueryFile(hDropInfo, nFileCount - 1, NULL, 0);

        int nRealLength = DragQueryFile(hDropInfo, nFileCount - 1,
            strFileName.GetBuffer(nFileNameLen + 1),
            nFileNameLen + 1);
        strFileName.ReleaseBuffer();

        ASSERT(nFileNameLen == nRealLength);

    }