C# ComTypes.STGMEDIUM类代码示例

        /// <summary>
        /// Gets the file list.
        /// </summary>
        /// <param name="this">The IDataObject instance.</param>
        /// <returns>The file list in the data object.</returns>
        public static List<string> GetFileList(this IDataObject @this)
        {
            //  Create the format object.
            var formatEtc = new FORMATETC();

            //  Set up the format object, based on CF_HDROP.
            formatEtc.cfFormat = (short)CLIPFORMAT.CF_HDROP;
            formatEtc.ptd = IntPtr.Zero;
            formatEtc.dwAspect = DVASPECT.DVASPECT_CONTENT;
            formatEtc.lindex = -1;
            formatEtc.tymed = TYMED.TYMED_HGLOBAL;

            //  Get the data.
            // ReSharper disable RedundantAssignment
            var storageMedium = new STGMEDIUM();
            // ReSharper restore RedundantAssignment
            @this.GetData(ref formatEtc, out storageMedium);

            var fileList = new List<string>();

            //  Things can get risky now.
            try
            {
                //  Get the handle to the HDROP.
                var hDrop = storageMedium.unionmember;
                if (hDrop == IntPtr.Zero)
                    throw new ArgumentException("Failed to get the handle to the drop data.");

                //  Get the count of the files in the operation.
                var fileCount = Shell32.DragQueryFile(hDrop, UInt32.MaxValue, null, 0);

                //  Go through each file.
                for (uint i = 0; i < fileCount; i++)
                {
                    //  Storage for the file name.
                    var fileNameBuilder = new StringBuilder(MaxPath);

                    //  Get the file name.
                    var result = Shell32.DragQueryFile(hDrop, i, fileNameBuilder, (uint)fileNameBuilder.Capacity);

                    //  If we have a valid result, add the file name to the list of files.
                    if (result != 0)
                        fileList.Add(fileNameBuilder.ToString());
                }

            }
            finally
            {
                Ole32.ReleaseStgMedium(ref storageMedium);
            }

            return fileList;
        }

        void System.Runtime.InteropServices.ComTypes.IDataObject.GetData(ref FORMATETC formatetc, out STGMEDIUM medium)
        {
            if (formatetc.cfFormat == (Int16)DataFormats.GetFormat(NativeMethods.CFSTR_FILECONTENTS).Id)
            m_lindex = formatetc.lindex;

              medium = new System.Runtime.InteropServices.ComTypes.STGMEDIUM();
              if (GetTymedUseable(formatetc.tymed)) {
            if (formatetc.cfFormat == (Int16)DataFormats.GetFormat(NativeMethods.CFSTR_FILECONTENTS).Id) {
              if ((formatetc.tymed & TYMED.TYMED_ISTREAM) != TYMED.TYMED_NULL) {
            medium.tymed = TYMED.TYMED_ISTREAM;
            // medium.unionmember = Marshal.GetComInterfaceForObject(GetFileContents(this.m_SelectedItems, formatetc.lindex), typeof(IStreamWrapper));
            medium.unionmember = NativeMethods.VirtualAlloc(IntPtr.Zero, new UIntPtr(1), NativeMethods.MEM_COMMIT, NativeMethods.PAGE_READWRITE);
            if (medium.unionmember == IntPtr.Zero) {
              throw new OutOfMemoryException();
            }

            try {
              ((System.Runtime.InteropServices.ComTypes.IDataObject)this).GetDataHere(ref formatetc, ref medium);
              return;
            } catch {
              NativeMethods.VirtualFree(medium.unionmember, new UIntPtr(1), NativeMethods.MEM_DECOMMIT);
              medium.unionmember = IntPtr.Zero;
              throw;
            }
              }
            } else {
              if ((formatetc.tymed & TYMED.TYMED_HGLOBAL) != TYMED.TYMED_NULL) {
            medium.tymed = TYMED.TYMED_HGLOBAL;
            medium.unionmember = NativeMethods.GlobalAlloc(NativeMethods.GHND | NativeMethods.GMEM_DDESHARE, 1);
            if (medium.unionmember == IntPtr.Zero) {
              throw new OutOfMemoryException();
            }

            try {
              ((System.Runtime.InteropServices.ComTypes.IDataObject)this).GetDataHere(ref formatetc, ref medium);
              return;
            } catch {
              NativeMethods.GlobalFree(new HandleRef((STGMEDIUM)medium, medium.unionmember));
              medium.unionmember = IntPtr.Zero;
              throw;
            }
              }
            }
            medium.tymed = formatetc.tymed;
            ((System.Runtime.InteropServices.ComTypes.IDataObject)this).GetDataHere(ref formatetc, ref medium);
              } else {
            Marshal.ThrowExceptionForHR(NativeMethods.DV_E_TYMED);
              }
        }

 public static object Convert(string format, ref STGMEDIUM medium)
 {
     if (medium.unionmember != IntPtr.Zero)
     {
         if (medium.tymed == TYMED.TYMED_HGLOBAL)
         {
             return ConvertHandle(format, new HandleRef(format, medium.unionmember));
         }
         if (medium.tymed == TYMED.TYMED_ISTREAM)
         {
             return ConvertStream(format, new HandleRef(format, medium.unionmember));
         }
         if (medium.tymed == TYMED.TYMED_GDI)
         {
             return ConvertBitmap(new HandleRef(format, medium.unionmember));
         }
     }
     return null;
 }

        void System.Runtime.InteropServices.ComTypes.IDataObject.GetData(ref System.Runtime.InteropServices.ComTypes.FORMATETC formatetc, out System.Runtime.InteropServices.ComTypes.STGMEDIUM medium)
        {
            if (formatetc.cfFormat == (Int16)DataFormats.GetFormat(Win32.NativeMethods.CFSTR_FILECONTENTS).Id)
                m_lindex = formatetc.lindex;

            medium = new System.Runtime.InteropServices.ComTypes.STGMEDIUM();
            if (GetTymedUseable(formatetc.tymed))
            {
                if ((formatetc.tymed & TYMED.TYMED_HGLOBAL) != TYMED.TYMED_NULL)
                {
                    medium.tymed = TYMED.TYMED_HGLOBAL;
                    medium.unionmember = Win32.NativeMethods.GlobalAlloc(Win32.NativeMethods.GHND | Win32.NativeMethods.GMEM_DDESHARE, 1);
                    if (medium.unionmember == IntPtr.Zero)
                    {
                        throw new OutOfMemoryException();
                    }
                    try
                    {
                        ((System.Runtime.InteropServices.ComTypes.IDataObject)this).GetDataHere(ref formatetc, ref medium);
                        return;
                    }
                    catch
                    {
                        Win32.NativeMethods.GlobalFree(new HandleRef((STGMEDIUM)medium, medium.unionmember));
                        medium.unionmember = IntPtr.Zero;
                        throw;
                    }
                }
                medium.tymed = formatetc.tymed;
                ((System.Runtime.InteropServices.ComTypes.IDataObject)this).GetDataHere(ref formatetc, ref medium);
            }
            else
            {
                Marshal.ThrowExceptionForHR(Win32.NativeMethods.DV_E_TYMED);
            }
        }

        void IComDataObject.GetData(ref FORMATETC formatetc, out STGMEDIUM medium) {
            Debug.WriteLineIf(CompModSwitches.DataObject.TraceVerbose, "GetData");
            if (innerData is OleConverter) {
                ((OleConverter)innerData).OleDataObject.GetData(ref formatetc, out medium);
                return;
            }

            medium = new STGMEDIUM();

            if (GetTymedUseable(formatetc.tymed)) {
                if ((formatetc.tymed & TYMED.TYMED_HGLOBAL) != 0) {
                    medium.tymed = TYMED.TYMED_HGLOBAL;
                    medium.unionmember = UnsafeNativeMethods.GlobalAlloc(NativeMethods.GMEM_MOVEABLE
                                                             | NativeMethods.GMEM_DDESHARE
                                                             | NativeMethods.GMEM_ZEROINIT,
                                                             1);
                    if (medium.unionmember == IntPtr.Zero) {
                        throw new OutOfMemoryException();
                    }
 
                    try {
                        ((IComDataObject)this).GetDataHere(ref formatetc, ref medium);
                    }
                    catch {
                        UnsafeNativeMethods.GlobalFree(new HandleRef(medium, medium.unionmember));
                        medium.unionmember = IntPtr.Zero;
                        throw;
                    }
                }
                else {
                    medium.tymed  = formatetc.tymed;
                    ((IComDataObject)this).GetDataHere(ref formatetc, ref medium);
                }
            }
            else {
                Marshal.ThrowExceptionForHR(DV_E_TYMED);
            }
        }

            /// <include file='doc\DataObject.uex' path='docs/doc[@for="DataObject.OleConverter.GetDataFromOleOther"]/*' />
            /// <devdoc>
            ///     Retrieves the specified format data from the bound IComDataObject, from
            ///     other sources that IStream and HGLOBAL... this is really just a place
            ///     to put the "special" formats like BITMAP, ENHMF, etc.
            /// </devdoc>
            /// <internalonly/>
            private Object GetDataFromOleOther(string format) {
                Debug.Assert(innerData != null, "You must have an innerData on all DataObjects");

                FORMATETC formatetc = new FORMATETC();
                STGMEDIUM medium = new STGMEDIUM();

                TYMED tymed = (TYMED)0;

                if (format.Equals(DataFormats.Bitmap)) {
                    tymed = TYMED.TYMED_GDI;
                }
                else if (format.Equals(DataFormats.EnhancedMetafile)) {
                    tymed = TYMED.TYMED_ENHMF;
                }

                if (tymed == (TYMED)0) {
                    return null;
                }

                formatetc.cfFormat = unchecked((short)(ushort)(DataFormats.GetFormat(format).Id));
                formatetc.dwAspect = DVASPECT.DVASPECT_CONTENT;
                formatetc.lindex = -1;
                formatetc.tymed = tymed;
                medium.tymed = tymed;

                Object data = null;
                if (NativeMethods.S_OK == QueryGetDataUnsafe(ref formatetc)) {
                    try {
                        IntSecurity.UnmanagedCode.Assert();
                        try {
                             innerData.GetData(ref formatetc, out medium);
                        }
                        finally {
                            CodeAccessPermission.RevertAssert();
                        }
                    }
                    catch {
                    }
                }

                if (medium.unionmember != IntPtr.Zero) {

                    if (format.Equals(DataFormats.Bitmap)
                        //||format.Equals(DataFormats.Dib))
                    ) { 
                        // as/urt 140870 -- GDI+ doesn't own this HBITMAP, but we can't
                        // delete it while the object is still around.  So we have to do the really expensive
                        // thing of cloning the image so we can release the HBITMAP.
                        //

                        //This bitmap is created by the com object which originally copied the bitmap to tbe 
                        //clipboard. We call Add here, since DeleteObject calls Remove.
                        System.Internal.HandleCollector.Add(medium.unionmember, NativeMethods.CommonHandles.GDI);
                        Image clipboardImage = null;
                        IntSecurity.ObjectFromWin32Handle.Assert();
                        try
                        {
                            clipboardImage = Image.FromHbitmap(medium.unionmember);
                        }
                        finally
                        {
                            CodeAccessPermission.RevertAssert();
                        }
                        if (clipboardImage != null) {
                            Image firstImage = clipboardImage;
                            clipboardImage = (Image)clipboardImage.Clone();
                            SafeNativeMethods.DeleteObject(new HandleRef(null, medium.unionmember));
                            firstImage.Dispose();
                        }
                        data = clipboardImage;
                    }
/* gpr:
                    else if (format.Equals(DataFormats.EnhancedMetafile)) {
                        data = new Metafile(medium.unionmember);
                    }
*/
                }

                return data;
            }

        /// <include file='doc\DataObject.uex' path='docs/doc[@for="DataObject.GetDataIntoOleStructs"]/*' />
        /// <devdoc>
        ///     Populates Ole datastructes from a [....] dataObject. This is the core
        ///     of [....] to OLE conversion.
        /// </devdoc>
        /// <internalonly/>
        private void GetDataIntoOleStructs(ref FORMATETC formatetc,
                                           ref STGMEDIUM medium) {

            if (GetTymedUseable(formatetc.tymed) && GetTymedUseable(medium.tymed)) {
                string format = DataFormats.GetFormat(formatetc.cfFormat).Name;

                if (GetDataPresent(format)) {
                    Object data = GetData(format);                    

                    if ((formatetc.tymed & TYMED.TYMED_HGLOBAL) != 0) {
                        int hr = SaveDataToHandle(data, format, ref medium);
                        if (NativeMethods.Failed(hr)) {
                            Marshal.ThrowExceptionForHR(hr);
                        }
                    }
                    else if ((formatetc.tymed & TYMED.TYMED_GDI) != 0) {
                        if (format.Equals(DataFormats.Bitmap) && data is Bitmap) {
                            // save bitmap
                            //
                            Bitmap bm = (Bitmap)data;
                            if (bm != null) {
                                medium.unionmember = GetCompatibleBitmap(bm); // gpr: Does this get properly disposed?
                            }
                        }
                    }
/* gpr
                    else if ((formatetc.tymed & TYMED.TYMED_ENHMF) != 0) {
                        if (format.Equals(DataFormats.EnhancedMetafile)
                            && data is Metafile) {
                            // save metafile

                            Metafile mf = (Metafile)data;
                            if (mf != null) {
                                medium.unionmember = mf.Handle;
                            }
                        }
                    } 
                    */
                    else {
                        Marshal.ThrowExceptionForHR (DV_E_TYMED);
                    }
                }
                else {
                    Marshal.ThrowExceptionForHR (DV_E_FORMATETC);
                }
            }
            else {
                Marshal.ThrowExceptionForHR (DV_E_TYMED);
            }
        }

        private ShellObject[] ParseShellIDListArray(System.Runtime.InteropServices.ComTypes.IDataObject pDataObj)
        {
            List<ShellObject> result = new List<ShellObject>();
            System.Runtime.InteropServices.ComTypes.FORMATETC format = new System.Runtime.InteropServices.ComTypes.FORMATETC();
            System.Runtime.InteropServices.ComTypes.STGMEDIUM medium = new System.Runtime.InteropServices.ComTypes.STGMEDIUM();

            format.cfFormat = (short)ExplorerBrowser.RegisterClipboardFormat("Shell IDList Array");
            format.dwAspect = System.Runtime.InteropServices.ComTypes.DVASPECT.DVASPECT_CONTENT;
            format.lindex = 0;
            format.ptd = IntPtr.Zero;
            format.tymed = System.Runtime.InteropServices.ComTypes.TYMED.TYMED_HGLOBAL;

            pDataObj.GetData(ref format, out medium);
            ExplorerBrowser.GlobalLock(medium.unionmember);

            try
            {
                ShellObject parentFolder = null;
                int count = Marshal.ReadInt32(medium.unionmember);
                int offset = 4;

                for (int n = 0; n <= count; ++n)
                {
                    int pidlOffset = Marshal.ReadInt32(medium.unionmember, offset);
                    int pidlAddress = (int)medium.unionmember + pidlOffset;

                    if (n == 0)
                    {
                        parentFolder = ShellObjectFactory.Create(new IntPtr(pidlAddress));
                    }
                    else
                    {
                        result.Add(ShellObjectFactory.Create(ExplorerBrowser.CreateItemWithParent(GetIShellFolder(parentFolder.NativeShellItem), new IntPtr(pidlAddress))));
                    }

                    offset += 4;
                }
            }
            finally
            {
                Marshal.FreeHGlobal(medium.unionmember);
            }

            return result.ToArray();
        }

            /// <include file='doc\DataObject.uex' path='docs/doc[@for="DataObject.OleConverter.GetDataFromOleHGLOBAL"]/*' />
            /// <devdoc>
            ///     Uses HGLOBALs and retrieves the specified format from the bound IComDatabject.
            /// </devdoc>
            /// <internalonly/>
            private Object GetDataFromOleHGLOBAL(string format) {
                Debug.Assert(innerData != null, "You must have an innerData on all DataObjects");

                FORMATETC formatetc = new FORMATETC();
                STGMEDIUM medium = new STGMEDIUM();

                formatetc.cfFormat = unchecked((short)(ushort)(DataFormats.GetFormat(format).Id));
                formatetc.dwAspect = DVASPECT.DVASPECT_CONTENT;
                formatetc.lindex = -1;
                formatetc.tymed = TYMED.TYMED_HGLOBAL;

                medium.tymed = TYMED.TYMED_HGLOBAL;

                object data = null;

                if (NativeMethods.S_OK == QueryGetDataUnsafe(ref formatetc)) {
                    try {
                        IntSecurity.UnmanagedCode.Assert();
                        try {
                             innerData.GetData(ref formatetc, out medium);
                        }
                        finally {
                            CodeAccessPermission.RevertAssert();
                        }

                        if (medium.unionmember != IntPtr.Zero) {
                            data = GetDataFromHGLOBLAL(format, medium.unionmember);
                        }
                    }
                    catch {
                    }
                }
                return data;
            }

 private int SaveDataToHandle(object data, string format, ref STGMEDIUM medium) {
     int hr = NativeMethods.E_FAIL;
     if (data is Stream) {
         hr = SaveStreamToHandle(ref medium.unionmember, (Stream)data);
     }
     else if (format.Equals(DataFormats.Text)
              || format.Equals(DataFormats.Rtf)
              || format.Equals(DataFormats.OemText)) {
         hr = SaveStringToHandle(medium.unionmember, data.ToString(), false);
     }
     else if (format.Equals(DataFormats.Html)) {
          hr = SaveHtmlToHandle(medium.unionmember, data.ToString());
     }
     else if (format.Equals(DataFormats.UnicodeText)) {
          hr = SaveStringToHandle(medium.unionmember, data.ToString(), true);
     }
     else if (format.Equals(DataFormats.FileDrop)) {
         hr = SaveFileListToHandle(medium.unionmember, (string[])data);
     }
     else if (format.Equals(CF_DEPRECATED_FILENAME)) {
         string[] filelist = (string[])data;
         hr = SaveStringToHandle(medium.unionmember, filelist[0], false);
     }
     else if (format.Equals(CF_DEPRECATED_FILENAMEW)) {
         string[] filelist = (string[])data;
         hr = SaveStringToHandle(medium.unionmember, filelist[0], true);
     }
     else if (format.Equals(DataFormats.Dib)
              && data is Image) {
         // GDI+ does not properly handle saving to DIB images.  Since the 
         // clipboard will take an HBITMAP and publish a Dib, we don't need
         // to support this.
         //
         hr = DV_E_TYMED; // SaveImageToHandle(ref medium.unionmember, (Image)data);
     }
     else if (format.Equals(DataFormats.Serializable)
              || data is ISerializable 
              || (data != null && data.GetType().IsSerializable)) {
         hr = SaveObjectToHandle(ref medium.unionmember, data);
     }
     return hr;
 }

 private static void GetMediumFromObject(object data, out STGMEDIUM medium)
 {
     MemoryStream memoryStream = new MemoryStream();
     memoryStream.Write(DataObjectExtensions.ManagedDataStamp.ToByteArray(), 0, Marshal.SizeOf(typeof(Guid)));
     BinaryFormatter binaryFormatter = new BinaryFormatter();
     binaryFormatter.Serialize((Stream)memoryStream, (object)data.GetType());
     binaryFormatter.Serialize((Stream)memoryStream, DataObjectExtensions.GetAsSerializable(data));
     byte[] buffer = memoryStream.GetBuffer();
     IntPtr num = Marshal.AllocHGlobal(buffer.Length);
     try
     {
         Marshal.Copy(buffer, 0, num, buffer.Length);
     }
     catch
     {
         Marshal.FreeHGlobal(num);
         throw;
     }
     medium.unionmember = num;
     medium.tymed = TYMED.TYMED_HGLOBAL;
     medium.pUnkForRelease = (object)null;
 }

		public void GetData(ref FORMATETC format, out STGMEDIUM medium)
		{
			ComDebug.ReportInfo("{0}.IDataObject.GetData({1})", this.GetType().Name, DataObjectHelper.FormatEtcToString(format));

			try
			{
				// Locate the data
				foreach (var rendering in Renderings)
				{
					if ((rendering.format.tymed & format.tymed) > 0
							&& rendering.format.dwAspect == format.dwAspect
							&& rendering.format.cfFormat == format.cfFormat
							&& rendering.renderer != null)
					{
						// Found it. Return a copy of the data.

						medium = new STGMEDIUM();
						medium.tymed = rendering.format.tymed & format.tymed;
						medium.unionmember = rendering.renderer(medium.tymed);
						if (medium.tymed == TYMED.TYMED_ISTORAGE || medium.tymed == TYMED.TYMED_ISTREAM)
							medium.pUnkForRelease = Marshal.GetObjectForIUnknown(medium.unionmember);
						else
							medium.pUnkForRelease = null;
						return;
					}
				}
			}
			catch (Exception e)
			{
				ComDebug.ReportError("{0}.IDataObject.GetData threw an exception {1}", this.GetType().Name, e);
				throw;
			}

			ComDebug.ReportInfo("{0}.IDataObject.GetData, no data delivered!", this.GetType().Name);
			medium = new STGMEDIUM();
			// Marshal.ThrowExceptionForHR(ComReturnValue.DV_E_FORMATETC);
		}

		public void SetData(ref FORMATETC formatIn, ref STGMEDIUM medium, bool release)
		{
			ComDebug.ReportError("{0}.IDataObject.SetData - NOT SUPPORTED!", this.GetType().Name);
			throw new NotSupportedException();
		}

        // Get this clipboard format out of this data object
        public static byte[] GetData(IDataObject oData, string cfFormat)
        {
            // First, we try using the built-in functionality. Unfortunately, in the TYMED_ISTREAM case
            // they forget to seek the stream to zero, and so aren't successful. We'll take care of that
            // in a moment.
            //
            System.IO.Stream stm = (System.IO.Stream)oData.GetData(cfFormat, false);
            if (null != stm)
                {
                stm.Seek(0, System.IO.SeekOrigin.Begin);
                int    cb  = (int)stm.Length;
                byte[] rgb = new byte[cb];
                int cbRead = stm.Read(rgb, 0, cb);
                if (cbRead == cb)
                    {
                    // The bug is that the data returned is entirely zero. Let's check.
                    //
                    for (int ib=0; ib < cb; ib++)
                        {
                        if (rgb[ib] != 0)
                            return rgb;
                        }
                    }
                }
            //
            // Ok, try to see if we can get it on a stream ourselves
            //
            COMTypes.IDataObject ido       = (COMTypes.IDataObject)oData;
            COMTypes.FORMATETC   formatEtc = new COMTypes.FORMATETC();
            COMTypes.STGMEDIUM   medium    = new COMTypes.STGMEDIUM();
            formatEtc.cfFormat = (short)DataFormats.GetFormat(cfFormat).Id;
            formatEtc.dwAspect = COMTypes.DVASPECT.DVASPECT_CONTENT;
            formatEtc.lindex   = -1;                            // REVIEW: is 0 better?
            formatEtc.tymed    = COMTypes.TYMED.TYMED_ISTREAM;
            //
            ido.GetData(ref formatEtc, out medium);
            //
            if (medium.unionmember != IntPtr.Zero)
                {
                // Get at the IStream and release the ref in the medium
                COMTypes.IStream istm = (COMTypes.IStream)Marshal.GetObjectForIUnknown(medium.unionmember);
                Marshal.Release(medium.unionmember);

                // How big is the stream?
                COMTypes.STATSTG statstg = new COMTypes.STATSTG();
                istm.Stat(out statstg, 1);
                int cb = (int)statstg.cbSize;
                byte[] rgb = new byte[cb];

                // Seek the stream to the beginning and read the data
                IntPtr pcbRead = Marshal.AllocCoTaskMem(sizeof(int));
                istm.Seek(0, 0, IntPtr.Zero);
                istm.Read(rgb, cb, pcbRead);
                int cbRead = Marshal.ReadInt32(pcbRead);
                Marshal.FreeCoTaskMem(pcbRead);

                if (cb==cbRead)
                    return rgb;
                }
            //
            // Can't get the data
            //
            return null;
        }

        internal static void GetSelectedItems(IntPtr pidlFolder, IntPtr pDataObj, IntPtr hKeyProgID, ref List<String> SelectedItems, ref bool isClickOnEmptyArea)
        {
            if (pDataObj == IntPtr.Zero && pidlFolder == IntPtr.Zero)
                throw new ArgumentException();
            else if (pDataObj == IntPtr.Zero)
            {
                //User Click on Empty Area of a Folder, pDataObj is empty while pidlFolder is the current path
                StringBuilder sb = new StringBuilder(260);
                if (!NativeMethods.SHGetPathFromIDListW(pidlFolder, sb))
                    Marshal.ThrowExceptionForHR(WinError.E_FAIL);
                else
                {
                    isClickOnEmptyArea = true;
                    SelectedItems = new List<string>();
                    SelectedItems.Add(sb.ToString());
                }
            }
            else
            {
                //User actually select some item, pDataObj is the list while pidlFolder is empty
                isClickOnEmptyArea = false;

                FORMATETC fe = new FORMATETC();
                fe.cfFormat = (short)CLIPFORMAT.CF_HDROP;
                fe.ptd = IntPtr.Zero;
                fe.dwAspect = DVASPECT.DVASPECT_CONTENT;
                fe.lindex = -1;
                fe.tymed = TYMED.TYMED_HGLOBAL;
                STGMEDIUM stm = new STGMEDIUM();

                IDataObject dataObject = (IDataObject)Marshal.GetObjectForIUnknown(pDataObj);
                dataObject.GetData(ref fe, out stm);

                try
                {
                    IntPtr hDrop = stm.unionmember;
                    if (hDrop == IntPtr.Zero)
                        throw new ArgumentException();

                    uint nFiles = NativeMethods.DragQueryFile(hDrop, UInt32.MaxValue, null, 0);

                    if (nFiles == 0)
                        Marshal.ThrowExceptionForHR(WinError.E_FAIL);

                    SelectedItems = new List<string>();

                    for (int i = 0; i < nFiles; i++)
                    {
                        StringBuilder sb = new StringBuilder(260);
                        if (NativeMethods.DragQueryFile(hDrop, (uint)i, sb, sb.Capacity) == 0)
                            Marshal.ThrowExceptionForHR(WinError.E_FAIL);
                        else
                            SelectedItems.Add(sb.ToString());
                    }
                }
                finally
                {
                    NativeMethods.ReleaseStgMedium(ref stm);
                }
            }
        }