C# Signature:

[DllImport("ole32.dll")]
static extern int OleCreateFromFile([In] ref Guid rclsid,
   [MarshalAs(UnmanagedType.LPWStr)] string lpszFileName, [In] ref Guid riid,
   uint renderopt, [In] ref FORMATETC pFormatEtc, IOleClientSite pClientSite,
   IStorage pStg, [MarshalAs(UnmanagedType.IUnknown)] out object ppvObj);