/// <summary>
/// Create an array of FileItem objects based on a data object that contains
/// FileContents
/// </summary>
/// <param name="dataObject">data object containing FileContents</param>
/// <returns>Array of FileItem objects. Returns null if the FileContents
/// could not be extracted from the passed dataObject</returns>
public static FileItem[] CreateArrayFromDataObject(IDataObject dataObject)
{
try
{
// get the ole data object
OleDataObject oleDataObject = OleDataObject.CreateFrom(dataObject);
if (oleDataObject == null)
{
Debug.Fail("Unable to access OleDataObject!");
return(null);
}
// get an array of file descriptors specifying the file contents
FileDescriptor[] fileDescriptors =
FileContentsHelper.GetFileDescriptors(dataObject);
// allocate a FileItem object for each descriptor
FileItem[] fileItems = new FileItem[fileDescriptors.Length];
// initialize the file items
for (int i = 0; i < fileDescriptors.Length; i++)
{
fileItems[i] = new FileItemFromFileContents(
fileDescriptors[i], oleDataObject, i);
}
// return the file items
return(fileItems);
}
// this is a sketchy operation involving all kinds of interop voodoo,
// if we fail in release mode it is likely due to a drop source giving
// us invalid or unexpected data -- handle this gracefully while
// logging the error
catch (Exception e)
{
Debug.Fail("Unexpected error accessing FileContents", e.Message);
return(null);
}
}
/// <summary>
/// Utility function to extract an array of file contents file descriptors from
/// an IDataObject instnace
/// </summary>
/// <param name="dataObject">data object to extract descriptors from</param>
/// <returns>array of file descriptors</returns>
public static FileDescriptor[] GetFileDescriptors(IDataObject dataObject)
{
// Use an OleDataObject
OleDataObject oleDataObject = OleDataObject.CreateFrom(dataObject);
if (oleDataObject == null)
{
const string message = "DataObject not valid for FileContents!";
Debug.Fail(message);
throw
new InvalidOperationException(message);
}
// Try to get the data as FileGroupDescriptorW then try to get it
// as FileGroupDescriptor
bool bFileNameIsWide;
OleStgMediumHGLOBAL stgMedium = (OleStgMediumHGLOBAL)oleDataObject.GetData(
DataFormatsEx.FileGroupDescriptorWFormat, TYMED.HGLOBAL);
if (stgMedium != null)
{
bFileNameIsWide = true;
}
else
{
stgMedium = (OleStgMediumHGLOBAL)oleDataObject.GetData(
DataFormatsEx.FileGroupDescriptorFormat, TYMED.HGLOBAL);
if (stgMedium != null)
{
bFileNameIsWide = false;
}
else
{
const string message = "File group descriptor not available!";
Debug.Fail(message);
throw
new InvalidOperationException(message);
}
}
// Copy the descriptors
using ( stgMedium )
{
using (HGlobalLock globalMem = new HGlobalLock(stgMedium.Handle))
{
// get a pointer to the count
IntPtr pCount = globalMem.Memory;
// determine the number of file descriptors
Int32 count = Marshal.ReadInt32(pCount);
// get a pointer to the descriptors
IntPtr pDescriptors =
new IntPtr(globalMem.Memory.ToInt32() + Marshal.SizeOf(count));
// allocate the array of structures that will be returned
FileDescriptor[] descriptors = new FileDescriptor[count];
// determine the sizes of the various data elements
const int FILENAME_BUFFER_SIZE = 260;
int headerSize = Marshal.SizeOf(typeof(FILEDESCRIPTOR_HEADER));
int fileNameSize = bFileNameIsWide ? FILENAME_BUFFER_SIZE * 2 : FILENAME_BUFFER_SIZE;
int totalSize = headerSize + fileNameSize;
// iterate through the memory block copying the FILEDESCRIPTOR structures
for (int i = 0; i < count; i++)
{
// determine the addresses of the various data elements
IntPtr pAddr = new IntPtr(pDescriptors.ToInt32() + (i * totalSize));
IntPtr pFileNameAddr = new IntPtr(pAddr.ToInt32() + headerSize);
// copy the header
descriptors[i].header = (FILEDESCRIPTOR_HEADER)
Marshal.PtrToStructure(pAddr, typeof(FILEDESCRIPTOR_HEADER));
// copy the file name (use Unicode or Ansi depending upon descriptor type)
if (bFileNameIsWide)
{
descriptors[i].fileName = Marshal.PtrToStringUni(pFileNameAddr);
}
else
{
descriptors[i].fileName = Marshal.PtrToStringAnsi(pFileNameAddr);
}
}
// return the descriptors
return(descriptors);
}
}
}