I'm trying to embed a PDF file into a Word document using the OLE technique described here: https://learn.microsoft.com/en-us/archive/blogs/brian_jones/embedding-any-file-type-like-pdf-in-an-open-xml-file
I've tried to implement the C++ code provided in C# so that the whole project's in one place and am almost there except for one roadblock. When I try to feed the generated OLE object binary data into the Word document I get an IOException.
IOException: The process cannot access the file 'C:\Wherever\Whatever.pdf.bin' because it is being used by another process.
There is a file handle open the .bin file ("oleOutputFileName" below) and I don't know how to get rid of it. I don't know a huge amount about COM - I'm winging it here - and I don't know where the file handle is or how to release it.
Here's what my C#-ised code looks like. What am I missing?
public void ExportOleFile(string oleOutputFileName, string emfOutputFileName)
{
OLE32.IStorage storage;
var result = OLE32.StgCreateStorageEx(
oleOutputFileName,
OLE32.STGM.STGM_READWRITE | OLE32.STGM.STGM_SHARE_EXCLUSIVE | OLE32.STGM.STGM_CREATE | OLE32.STGM.STGM_TRANSACTED,
OLE32.STGFMT.STGFMT_DOCFILE,
0,
IntPtr.Zero,
IntPtr.Zero,
ref OLE32.IID_IStorage,
out storage
);
var CLSID_NULL = Guid.Empty;
OLE32.IOleObject pOle;
result = OLE32.OleCreateFromFile(
ref CLSID_NULL,
_inputFileName,
ref OLE32.IID_IOleObject,
OLE32.OLERENDER.OLERENDER_NONE,
IntPtr.Zero,
null,
storage,
out pOle
);
result = OLE32.OleRun(pOle);
IntPtr unknownFromOle = Marshal.GetIUnknownForObject(pOle);
IntPtr unknownForDataObj;
Marshal.QueryInterface(unknownFromOle, ref OLE32.IID_IDataObject, out unknownForDataObj);
var pdo = Marshal.GetObjectForIUnknown(unknownForDataObj) as IDataObject;
var fetc = new FORMATETC();
fetc.cfFormat = (short)OLE32.CLIPFORMAT.CF_ENHMETAFILE;
fetc.dwAspect = DVASPECT.DVASPECT_CONTENT;
fetc.lindex = -1;
fetc.ptd = IntPtr.Zero;
fetc.tymed = TYMED.TYMED_ENHMF;
var stgm = new STGMEDIUM();
stgm.unionmember = IntPtr.Zero;
stgm.tymed = TYMED.TYMED_ENHMF;
pdo.GetData(ref fetc, out stgm);
var hemf = GDI32.CopyEnhMetaFile(stgm.unionmember, emfOutputFileName);
storage.Commit((int)OLE32.STGC.STGC_DEFAULT);
pOle.Close(0);
GDI32.DeleteEnhMetaFile(stgm.unionmember);
GDI32.DeleteEnhMetaFile(hemf);
}
UPDATE 1: Clarified which file I meant by "the .bin file".
UPDATE 2: I'm not using "using" blocks because the things I want to get rid of aren't disposable. (And to be perfectly honest I'm not sure what I need to release to remove the file handle, COM being a foreign language to me.)
I found the answer and it's pretty simple. (Probably too simple - it feels like a hack but since I know so little about COM programming I'm just going to go with it.)
The storage object had multiple references on it, so just keep going until they're all gone: