public int DragOver(int grfKeyState, Point pt, ref DragDropEffects pdwEffect)
 {
     if (pt != pointLastDrag)
     {
         pointLastDrag = pt;
         parent.OnDragOver(pt);
     }
     return(passthrough.DragOver(grfKeyState, pt, ref pdwEffect));
 }
        public int DragDrop(System.Runtime.InteropServices.ComTypes.IDataObject pDataObj, int grfKeyState, BandObjectLib.POINT pt, ref DragDropEffects pdwEffect)
        {
            try {
                if (this.DragFileOver != null)
                {
                    DragEventArgs e = new DragEventArgs(null, grfKeyState, pt.x, pt.y, DragDropEffects.Move | DragDropEffects.Copy | DragDropEffects.Scroll, pdwEffect);
                    this.DragFileOver(null, e);
                    pdwEffect = e.Effect;
                }
                else
                {
                    pdwEffect = DragDropEffects.Copy;
                }
                if (pdwEffect != DragDropEffects.None)
                {
                    if (this.DragFileDrop != null)
                    {
                        IntPtr ptr;
                        byte[] buffer;
                        switch (this.DragFileDrop(out ptr, out buffer))
                        {
                        case -1:
                            return(0);

                        case 0: {
                            IShellFolder ppv   = null;
                            object       obj2  = null;
                            Guid         riid  = ExplorerGUIDs.IID_IShellFolder;
                            Guid         guid2 = ExplorerGUIDs.IID_IDropTarget;
                            using (IDLWrapper wrapper = new IDLWrapper(buffer)) {
                                if (wrapper.Available && wrapper.IsDropTarget)
                                {
                                    try {
                                        IntPtr ptr2;
                                        if (PInvoke.SHBindToParent(wrapper.PIDL, riid, out ppv, out ptr2) == 0)
                                        {
                                            uint     rgfReserved = 0;
                                            IntPtr[] apidl       = new IntPtr[] { ptr2 };
                                            if (ppv.GetUIObjectOf(ptr, 1, apidl, ref guid2, ref rgfReserved, out obj2) == 0)
                                            {
                                                _IDropTarget target = obj2 as _IDropTarget;
                                                if (target != null)
                                                {
                                                    DragDropEffects effects = pdwEffect;
                                                    if (target.DragEnter(pDataObj, this.iLastKeyState, pt, ref effects) == 0)
                                                    {
                                                        effects = pdwEffect;
                                                        if (target.DragOver(this.iLastKeyState, pt, ref effects) == 0)
                                                        {
                                                            if ((this.iLastKeyState & 2) != 0)
                                                            {
                                                                pdwEffect = DragDropEffects.Link | DragDropEffects.Move | DragDropEffects.Copy;
                                                            }
                                                            return(target.DragDrop(pDataObj, this.iLastKeyState, pt, ref pdwEffect));
                                                        }
                                                    }
                                                }
                                            }
                                        }
                                    }
                                    catch {
                                    }
                                    finally {
                                        if (ppv != null)
                                        {
                                            Marshal.ReleaseComObject(ppv);
                                        }
                                        if (obj2 != null)
                                        {
                                            Marshal.ReleaseComObject(obj2);
                                        }
                                        if (this.DragDropEnd != null)
                                        {
                                            this.DragDropEnd(this, EventArgs.Empty);
                                        }
                                    }
                                }
                            }
                            return(0);
                        }
                        }
                    }
                    FORMATETC format = new FORMATETC();
                    format.cfFormat = 15;
                    format.ptd      = IntPtr.Zero;
                    format.dwAspect = DVASPECT.DVASPECT_CONTENT;
                    format.lindex   = -1;
                    format.tymed    = TYMED.TYMED_HGLOBAL;
                    STGMEDIUM medium = new STGMEDIUM();
                    try {
                        pDataObj.GetData(ref format, out medium);
                        PInvoke.SendMessage(this.hwnd, 0x233, medium.unionmember, IntPtr.Zero);
                    }
                    catch {
                    }
                    finally {
                        PInvoke.ReleaseStgMedium(ref medium);
                    }
                }
            }
            finally {
                if (pDataObj != null)
                {
                    Marshal.FinalReleaseComObject(pDataObj);
                }
            }
            return(0);
        }