private static void ReadIStorageIntoStream(IntPtr handle, Stream stream)
{
//To handle a IStorage it needs to be written into a second unmanaged memory mapped storage
//and then the data can be read from memory into a managed byte and returned as a MemoryStream
NativeMethods.ILockBytes iLockBytes = null;
NativeMethods.IStorage iStorageNew = null;
IntPtr ptrRead = IntPtr.Zero;
try
{
//Marshal pointer to an IStorage object
NativeMethods.IStorage iStorage = (NativeMethods.IStorage)Marshal.GetObjectForIUnknown(handle);
//Create an ILockBytes object on a HGlobal, then create a IStorage object on top of the ILockBytes object
iLockBytes = NativeMethods.CreateILockBytesOnHGlobal(IntPtr.Zero, true);
iStorageNew = NativeMethods.StgCreateDocfileOnILockBytes(iLockBytes, 0x00001012, 0);
//Copy the IStorage object into the new IStorage object
iStorage.CopyTo(0, null, IntPtr.Zero, iStorageNew);
iLockBytes.Flush();
iStorageNew.Commit(0);
//Get length of ILockBytes byte array
System.Runtime.InteropServices.ComTypes.STATSTG stat = new System.Runtime.InteropServices.ComTypes.STATSTG();
iLockBytes.Stat(out stat, 1);
long length = stat.cbSize;
//Read bytes into stream
ptrRead = Marshal.AllocCoTaskMem(sizeof(int));
byte[] buffer = new byte[4096]; //4 KB buffer
int offset = 0;
int bytesRead;
while (true)
{
iLockBytes.ReadAt(offset, buffer, buffer.Length, ptrRead);
bytesRead = Marshal.ReadInt32(ptrRead);
if (bytesRead == 0)
{
break;
}
stream.Write(buffer, 0, bytesRead);
offset += bytesRead;
}
}
finally
{
//Release all unmanaged objects
Marshal.FreeCoTaskMem(ptrRead);
if (iStorageNew != null)
{
Marshal.ReleaseComObject(iStorageNew);
}
if (iLockBytes != null)
{
Marshal.ReleaseComObject(iLockBytes);
}
}
}
/// <summary>
/// Retrieves the data associated with the specified data format at the specified index.
/// </summary>
/// <param name="format">The format of the data to retrieve. See <see cref="T:System.Windows.Forms.DataFormats"></see> for predefined formats.</param>
/// <param name="index">The index of the data to retrieve.</param>
/// <returns>
/// A <see cref="MemoryStream"/> containing the raw data for the specified data format at the specified index.
/// </returns>
public MemoryStream GetData(string format, int index)
{
//create a FORMATETC struct to request the data with
FORMATETC formatetc = new FORMATETC();
formatetc.cfFormat = (short)DataFormats.GetDataFormat(format).Id;
formatetc.dwAspect = DVASPECT.DVASPECT_CONTENT;
formatetc.lindex = index;
formatetc.ptd = new IntPtr(0);
formatetc.tymed = TYMED.TYMED_ISTREAM | TYMED.TYMED_ISTORAGE | TYMED.TYMED_HGLOBAL;
//create STGMEDIUM to output request results into
STGMEDIUM medium = new STGMEDIUM();
//using the Com IDataObject interface get the data using the defined FORMATETC
this.comUnderlyingDataObject.GetData(ref formatetc, out medium);
//retrieve the data depending on the returned store type
switch (medium.tymed)
{
case TYMED.TYMED_ISTORAGE:
//to handle a IStorage it needs to be written into a second unmanaged
//memory mapped storage and then the data can be read from memory into
//a managed byte and returned as a MemoryStream
NativeMethods.IStorage iStorage = null;
NativeMethods.IStorage iStorage2 = null;
NativeMethods.ILockBytes iLockBytes = null;
System.Runtime.InteropServices.ComTypes.STATSTG iLockBytesStat;
try
{
//marshal the returned pointer to a IStorage object
iStorage = (NativeMethods.IStorage)Marshal.GetObjectForIUnknown(medium.unionmember);
Marshal.Release(medium.unionmember);
//create a ILockBytes (unmanaged byte array) and then create a IStorage using the byte array as a backing store
iLockBytes = NativeMethods.CreateILockBytesOnHGlobal(IntPtr.Zero, true);
iStorage2 = NativeMethods.StgCreateDocfileOnILockBytes(iLockBytes, 0x00001012, 0);
//copy the returned IStorage into the new IStorage
iStorage.CopyTo(0, null, IntPtr.Zero, iStorage2);
iLockBytes.Flush();
iStorage2.Commit(0);
//get the STATSTG of the ILockBytes to determine how many bytes were written to it
iLockBytesStat = new System.Runtime.InteropServices.ComTypes.STATSTG();
iLockBytes.Stat(out iLockBytesStat, 1);
int iLockBytesSize = (int)iLockBytesStat.cbSize;
//read the data from the ILockBytes (unmanaged byte array) into a managed byte array
byte[] iLockBytesContent = new byte[iLockBytesSize];
iLockBytes.ReadAt(0, iLockBytesContent, iLockBytesContent.Length, null);
//wrapped the managed byte array into a memory stream and return it
return(new MemoryStream(iLockBytesContent));
}
finally
{
//release all unmanaged objects
Marshal.ReleaseComObject(iStorage2);
Marshal.ReleaseComObject(iLockBytes);
Marshal.ReleaseComObject(iStorage);
}
case TYMED.TYMED_ISTREAM:
//to handle a IStream it needs to be read into a managed byte and
//returned as a MemoryStream
IStream iStream = null;
System.Runtime.InteropServices.ComTypes.STATSTG iStreamStat;
try
{
//marshal the returned pointer to a IStream object
iStream = (IStream)Marshal.GetObjectForIUnknown(medium.unionmember);
Marshal.Release(medium.unionmember);
//get the STATSTG of the IStream to determine how many bytes are in it
iStreamStat = new System.Runtime.InteropServices.ComTypes.STATSTG();
iStream.Stat(out iStreamStat, 0);
int iStreamSize = (int)iStreamStat.cbSize;
//read the data from the IStream into a managed byte array
byte[] iStreamContent = new byte[iStreamSize];
iStream.Read(iStreamContent, iStreamContent.Length, IntPtr.Zero);
//wrapped the managed byte array into a memory stream and return it
return(new MemoryStream(iStreamContent));
}
finally
{
//release all unmanaged objects
Marshal.ReleaseComObject(iStream);
}
case TYMED.TYMED_HGLOBAL:
//to handle a HGlobal the exisitng "GetDataFromHGLOBLAL" method is invoked via
//reflection
return((MemoryStream)this.getDataFromHGLOBLALMethod.Invoke(this.oleUnderlyingDataObject, new object[] { DataFormats.GetDataFormat((short)formatetc.cfFormat).Name, medium.unionmember }));
}
return(null);
}
private static void ReadIStorageIntoStream(IntPtr handle, Stream stream)
{
//To handle a IStorage it needs to be written into a second unmanaged memory mapped storage
//and then the data can be read from memory into a managed byte and returned as a MemoryStream
NativeMethods.IStorage iStorage = null;
NativeMethods.IStorage iStorage2 = null;
NativeMethods.ILockBytes iLockBytes = null;
System.Runtime.InteropServices.ComTypes.STATSTG iLockBytesStat;
try
{
//Marshal the returned pointer to a IStorage object
iStorage = (NativeMethods.IStorage)Marshal.GetObjectForIUnknown(handle);
Marshal.Release(handle);
//Create a ILockBytes (unmanaged byte array) and then create a IStorage using the byte array as a backing store
iLockBytes = NativeMethods.CreateILockBytesOnHGlobal(IntPtr.Zero, true);
iStorage2 = NativeMethods.StgCreateDocfileOnILockBytes(iLockBytes, 0x00001012, 0);
//Copy the returned IStorage into the new IStorage
iStorage.CopyTo(0, null, IntPtr.Zero, iStorage2);
iLockBytes.Flush();
iStorage2.Commit(0);
//Get the STATSTG of the ILockBytes to determine how many bytes were written to it
iLockBytesStat = new System.Runtime.InteropServices.ComTypes.STATSTG();
iLockBytes.Stat(out iLockBytesStat, 1);
int iLockBytesSize = (int)iLockBytesStat.cbSize;
//Read the data from the ILockBytes (unmanaged byte array) into a managed byte array
//byte[] iLockBytesContent = new byte[iLockBytesSize];
//iLockBytes.ReadAt(0, iLockBytesContent, iLockBytesContent.Length, null);
//Read bytes into stream
IntPtr ptrRead = Marshal.AllocCoTaskMem(Marshal.SizeOf(typeof(int)));
byte[] buffer = new byte[1024];
int offset = 0;
int bytesRead;
while (true)
{
iLockBytes.ReadAt(offset, buffer, buffer.Length, ptrRead);
bytesRead = Marshal.ReadInt32(ptrRead);
if (bytesRead == 0)
{
break;
}
stream.Write(buffer, 0, bytesRead);
offset += bytesRead;
}
stream.Seek(0, SeekOrigin.Begin);
//Wrap the managed byte array into a memory stream and return it
//return new MemoryStream(iLockBytesContent);
}
finally
{
//release all unmanaged objects
Marshal.ReleaseComObject(iStorage2);
Marshal.ReleaseComObject(iLockBytes);
Marshal.ReleaseComObject(iStorage);
}
}
public MemoryStream GetData(string format, int index)
{
FORMATETC formatetc = new FORMATETC()
{
cfFormat = (short)DataFormats.GetDataFormat(format).Id,
dwAspect = DVASPECT.DVASPECT_CONTENT,
lindex = index,
ptd = new IntPtr(0),
tymed = TYMED.TYMED_ISTREAM | TYMED.TYMED_ISTORAGE | TYMED.TYMED_HGLOBAL
};
STGMEDIUM medium = new STGMEDIUM();
this.comUnderlyingDataObject.GetData(ref formatetc, out medium);
switch (medium.tymed)
{
case TYMED.TYMED_ISTORAGE:
NativeMethods.IStorage iStorage = null;
NativeMethods.IStorage iStorage2 = null;
NativeMethods.ILockBytes iLockBytes = null;
System.Runtime.InteropServices.ComTypes.STATSTG iLockBytesStat;
try
{
iStorage = (NativeMethods.IStorage)Marshal.GetObjectForIUnknown(medium.unionmember);
Marshal.Release(medium.unionmember);
iLockBytes = NativeMethods.CreateILockBytesOnHGlobal(IntPtr.Zero, true);
iStorage2 = NativeMethods.StgCreateDocfileOnILockBytes(iLockBytes, 0x00001012, 0);
iStorage.CopyTo(0, null, IntPtr.Zero, iStorage2);
iLockBytes.Flush();
iStorage2.Commit(0);
iLockBytesStat = new System.Runtime.InteropServices.ComTypes.STATSTG();
iLockBytes.Stat(out iLockBytesStat, 1);
int iLockBytesSize = (int)iLockBytesStat.cbSize;
byte[] iLockBytesContent = new byte[iLockBytesSize];
iLockBytes.ReadAt(0, iLockBytesContent, iLockBytesContent.Length, null);
return(new MemoryStream(iLockBytesContent));
}
finally
{
Marshal.ReleaseComObject(iStorage2);
Marshal.ReleaseComObject(iLockBytes);
Marshal.ReleaseComObject(iStorage);
}
case TYMED.TYMED_ISTREAM:
IStream iStream = null;
System.Runtime.InteropServices.ComTypes.STATSTG iStreamStat;
try
{
iStream = (IStream)Marshal.GetObjectForIUnknown(medium.unionmember);
Marshal.Release(medium.unionmember);
iStreamStat = new System.Runtime.InteropServices.ComTypes.STATSTG();
iStream.Stat(out iStreamStat, 0);
int iStreamSize = (int)iStreamStat.cbSize;
byte[] iStreamContent = new byte[iStreamSize];
iStream.Read(iStreamContent, iStreamContent.Length, IntPtr.Zero);
return(new MemoryStream(iStreamContent));
}
finally
{
Marshal.ReleaseComObject(iStream);
}
case TYMED.TYMED_HGLOBAL:
return((MemoryStream)this.getDataFromHGLOBALMethod.Invoke(this.oleUnderlyingDataObject, new object[] { DataFormats.GetDataFormat((short)formatetc.cfFormat).Name, medium.unionmember }));
}
return(null);
}