CustomDragDropTarget.cs

//Drop target that will contain the custom drag and drop implementation for the given object
public MyDropTarget myDropTarget = null; //PS: Do not forget to dispose of it (we do it in Form1_FormClosed)

//Method where the myDropTarget is initialized
void InitializePagesViewAsDropTarget()
{
	PDFXEdit.IUIX_Obj obj = pdfCtl.Doc.ActiveView.PagesView.Obj;
	//Setting style of the object so it will accept dropping
	obj.SetStyleEx((int)PDFXEdit.UIX_ObjStyleExFlags.UIX_ObjStyleEx_DropTarget, (int)PDFXEdit.UIX_ObjStyleExFlags.UIX_ObjStyleEx_DropTarget);

	//Creating the drop target and filling it's supported formats
	myDropTarget = new MyDropTarget(obj, this);
	myDropTarget.AddSuppTextDrop(false);
	myDropTarget.AddSuppTextDrop(true);
}


//Class that implements the drop target functionality for the needed object
//In this example the PagesView was used as the "needed object"
public partial class MyDropTarget :
	PDFXEdit.IUIX_ObjImpl,
	PDFXEdit.IDropTarget,
	IDisposable
{
	//Here we push implementation of drag and drop functions of the PagesView
	public MyDropTarget(PDFXEdit.IUIX_Obj obj, MainFrm parentForm)
	{
		Obj_ = obj;
		if (Obj_ != null)
			Obj_.PushImpl(this);
		Parent = parentForm;
	}
	~MyDropTarget()
	{
		Dispose();
	}
	//Disposing of all of the links we made with objects and parent
	public void Dispose()
	{
		Parent = null;
		if (Disposed_)
			return;
		Disposed_ = true;
		if (Obj_ != null)
		{
			Obj_.PopImpl(this);
			System.Runtime.InteropServices.Marshal.ReleaseComObject(Obj_);
			Obj_ = null;
		}
	}

	//Main form - a parent that in our case holds the PDFXEdit control
	public MainFrm Parent = null;
	//Object for which we are implementing drag and drop
	public PDFXEdit.IUIX_Obj Obj_;
	//Used for single dispose control
	private bool Disposed_ = false;
	//Used for checking whether the DragEnter function gave successful results (formats check) - used in DragOver function
	private bool SuccessEnter = false;
	//List of supported formats that will be dragged onto our object
	List<System.Runtime.InteropServices.ComTypes.FORMATETC> m_SuppFmtEtc = new List<System.Runtime.InteropServices.ComTypes.FORMATETC>();

	// IUIX_ObjImpl
	public PDFXEdit.IUIX_Obj Obj
	{
		get { return this.Obj_; }
	}

	//Event listener that listens for e_QueryDropTarget
	public void OnEvent(PDFXEdit.IUIX_Obj pSender, PDFXEdit.IUIX_Event pEvent)
	{
		pEvent.Handled = false;

		if (pEvent.Code == (int)PDFXEdit.UIX_EventCodes.e_QueryDropTarget)
		{
			pEvent.Handled = true;
			IntPtr res = IntPtr.Zero;
			try
			{
				//We need to return com interface for PDFXEdit.IDropTarget from the current class as a pEvent.Result
				res = System.Runtime.InteropServices.Marshal.GetComInterfaceForObject(this, typeof(PDFXEdit.IDropTarget));
			}
			catch (Exception e)
			{
				Debug.WriteLine("pdfCtl.OnEvent: e.nEventID=={0}", e.Message);
			}

			if (res != IntPtr.Zero)
				pEvent.Result = (uint)res; // = (long)res for x64
		}
		else if (pEvent.Code == (int)PDFXEdit.UIX_EventCodes.e_BeforeDestroy)
		{
			Dispose();
		}
		else if (pEvent.Code == (int)PDFXEdit.UIX_EventCodes.e_Last)
		{
			Dispose();
		}
	}

	//Method that adds text support formats into the m_SuppFmtEtc
	public bool AddSuppTextDrop(bool bUnicode)
	{
		System.Runtime.InteropServices.ComTypes.FORMATETC FmtEtc = new System.Runtime.InteropServices.ComTypes.FORMATETC();
		if (bUnicode == false)
			FmtEtc.cfFormat = 1; //CF_TEXT
		else
			FmtEtc.cfFormat = 13; //CF_UNICODETEXT
		FmtEtc.dwAspect = System.Runtime.InteropServices.ComTypes.DVASPECT.DVASPECT_CONTENT;
		FmtEtc.lindex = -1;
		FmtEtc.tymed = System.Runtime.InteropServices.ComTypes.TYMED.TYMED_HGLOBAL;

		return AddSuppFmt(FmtEtc);
	}
	//Method that adds a new format into the m_SuppFmtEtc
	public bool AddSuppFmt(System.Runtime.InteropServices.ComTypes.FORMATETC FmtEtc)
	{
		if (FmtEtc.cfFormat == 0)
			return false;
		for (int i = 0; i < m_SuppFmtEtc.Count(); i++)
		{
			if (FmtEtc.cfFormat == m_SuppFmtEtc[i].cfFormat)
			{
				m_SuppFmtEtc[i] = FmtEtc;
				return true;
			}
		}
		m_SuppFmtEtc.Add(FmtEtc);
		return true;
	}

	//Method that gets FORMATETC and STGMEDIUM from the IDataObject
	public bool GetFormatAndStgMedium(PDFXEdit.IDataObject pDataObj, ref System.Runtime.InteropServices.ComTypes.FORMATETC fmt, ref System.Runtime.InteropServices.ComTypes.STGMEDIUM med)
	{
		//Running through the m_SuppFmtEtc and checking whether the dragged IDataObject is correct for one of them
		System.Runtime.InteropServices.ComTypes.IDataObject obj = (System.Runtime.InteropServices.ComTypes.IDataObject)pDataObj;
		for (int i = 0; i < m_SuppFmtEtc.Count(); i++)
		{
			try
			{
				//Getting STGMEDIUM data from IDataObject with the FORMATETC from the current iteration
				obj.GetData(m_SuppFmtEtc[i], out med);
				if (med.tymed != System.Runtime.InteropServices.ComTypes.TYMED.TYMED_NULL)
				{
					fmt = m_SuppFmtEtc[i];
					return true;
				}
			}
			catch (Exception e)
			{
				Debug.WriteLine("pdfCtl.OnEvent: e.nEventID=={0}", e.Message);
			}
		}
		return false;
	}

	public void OnPostEvent(PDFXEdit.IUIX_Obj pSender, PDFXEdit.IUIX_Event pEvent)
	{

	}

	public void OnPreEvent(PDFXEdit.IUIX_Obj pSender, PDFXEdit.IUIX_Event pEvent)
	{

	}

	/// <summary>
	/// Provides access to Win32-level constants, structures, and functions.
	/// </summary>
	[DllImport("Kernel32.dll", SetLastError = true)]
	private static extern IntPtr GlobalLock(IntPtr hMem);

	[DllImport("Kernel32.dll", SetLastError = true)]
	[return: MarshalAs(UnmanagedType.Bool)]
	private static extern bool GlobalUnlock(IntPtr hMem);

	[DllImport("Kernel32.dll", SetLastError = true)]
	private static extern int GlobalSize(IntPtr hMem);
	//


	public void DragEnter(PDFXEdit.IDataObject pDataObj, uint grfKeyState, PDFXEdit._POINTL pt, ref uint pdwEffect)
	{
		pdwEffect = (uint)DragDropEffects.None;
		SuccessEnter = false;
		System.Runtime.InteropServices.ComTypes.FORMATETC fmtEtc = new System.Runtime.InteropServices.ComTypes.FORMATETC();
		System.Runtime.InteropServices.ComTypes.STGMEDIUM medium = new System.Runtime.InteropServices.ComTypes.STGMEDIUM();
		//Getting FORMATETC and STGMEDIUM from the IDataObject
		if (GetFormatAndStgMedium(pDataObj, ref fmtEtc, ref medium) == true)
		{
			//If we succeeded then doing the page hit test
			//PDFXEdit.PXC_Point ptn = new PDFXEdit.PXC_Point();
			//if (Parent.HitTestPage(pt, out ptn) >= 0)
				pdwEffect = (uint)DragDropEffects.Copy; //If we are on a page then changing the cursor
			SuccessEnter = true;
		}
	}

	public void DragLeave()
	{
		SuccessEnter = false;
	}

	public void DragOver(uint grfKeyState, PDFXEdit._POINTL pt, ref uint pdwEffect)
	{
		pdwEffect = (uint)DragDropEffects.None;
		//If we got valid FORMATETC and STGMEDIUM in the DragEnter method then we can do the page hit test
		if (SuccessEnter != false)
		{
			//PDFXEdit.PXC_Point ptn = new PDFXEdit.PXC_Point();
			//if (Parent.HitTestPage(pt, out ptn) >= 0)
				pdwEffect = (uint)DragDropEffects.Copy;
		}
	}

	public void Drop(PDFXEdit.IDataObject pDataObj, uint grfKeyState, PDFXEdit._POINTL pt, ref uint pdwEffect)
	{
		SuccessEnter = false;
		System.Runtime.InteropServices.ComTypes.FORMATETC fmtEtc = new System.Runtime.InteropServices.ComTypes.FORMATETC();
		System.Runtime.InteropServices.ComTypes.STGMEDIUM medium = new System.Runtime.InteropServices.ComTypes.STGMEDIUM();
		//Getting FORMATETC and STGMEDIUM from the IDataObject
		if (GetFormatAndStgMedium(pDataObj, ref fmtEtc, ref medium) == true)
		{
			//If it's a global drag and drop and we've got the correct data
			if (medium.tymed == System.Runtime.InteropServices.ComTypes.TYMED.TYMED_HGLOBAL)
			{
				//Getting data from the STGMEDIUM
				var ptr = GlobalLock(medium.unionmember);
				if (ptr != IntPtr.Zero)
				{
					try
					{
						var length = (Int32)GlobalSize(ptr);
						var data = new byte[length];
						Marshal.Copy(ptr, data, 0, length);
						//Now we have a result string that has our dragged text
						string result = System.Text.Encoding.UTF8.GetString(data).TrimEnd('\0');
						//Adding Text annotation that contains that text
						Parent.AddAnnotFromText(pt, result);
					}
					finally
					{
						GlobalUnlock(medium.unionmember);
					}
				}
			}
		}
	}
}