OleSaveToStream

[System.Runtime.InteropServices.DllImport("OLE32.DLL", EntryPoint = "CreateStreamOnHGlobal")] // Create a COM stream from a pointer in unmanaged memory extern public static int CreateStreamOnHGlobal(IntPtr ptr, bool delete, out System.Runtime.InteropServices.ComTypes.IStream pOutStm);

[DllImport("OLE32.DLL", ExactSpelling = true, PreserveSig = false)] private static extern void OleSaveToStream(IPersistStreamInit pPStm, IStream pStm);

public int ByteSizeOfIPStreamInit(IPersistStreamInit pPersistStream) { int iSzOfStreamInBytes=0; IntPtr ptrIStream = IntPtr.Zero; IStream IPtrStream;

if (CreateStreamOnHGlobal(ptrIStream, true, out IPtrStream) == 0) { OleSaveToStream(pPersistStream,IPtrStream); iSzOfStreamInBytes = IStreamSizeRead(IPtrStream); } return (iSzOfStreamInBytes * 2); // (Multiply By 2 because Int32 is 4 bytes; Use caution.) }

public int IStreamSizeRead(IStream pOutStm) { pOutStm.Seek(0, 0, IntPtr.Zero);// Get size of the stream and read its contents to a byte array. System.Runtime.InteropServices.ComTypes.STATSTG fileinfo; pOutStm.Stat(out fileinfo, 0); byte[] data = new byte[fileinfo.cbSize]; int sizeOfInt32 = Marshal.SizeOf(typeof(int)); IntPtr pRead = Marshal.AllocHGlobal(sizeOfInt32); pOutStm.Read(data, data.Length, pRead); int read = Marshal.ReadInt32(pRead); Marshal.FreeHGlobal(pRead); return (data.Length); }