Shell Style Drag and Drop in .NET (WPF and WinForms)

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

gcadmes — Thu, 10 Apr 2008 04:06:12 GMT

Unsupported functions...

Can I get a little code snippet or help for adding the necessarry implementation for the unsupported functions?

thx

Greg

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Thu, 10 Apr 2008 19:37:10 GMT

Which functions in particular are you looking for help with? I added support for IDataObject.DAdvise and IDataObject.DUnadvise in Part 3 (http://blogs.msdn.com/adamroot/pages/shell-style-drag-and-drop-in-net-part-3.aspx).

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

gcadmes — Fri, 25 Apr 2008 01:18:51 GMT

Hi Adam,

What I am trying to do is drag a compressed archive file from a utility I wrote onto Explorer. I found a CodeProject artical where this is possible, but it doesn't seem to work well in Vista. It accomplishes this by using the IDataObject.GetDataHere method. That is why I requested the unsupported functions.

http://www.codeproject.com/KB/dotnet/DataObjectEx.aspx

My hope is to use the great example you provided and modify it to fit my needs.

Thanks for replying so quickly.

Cheers,

Greg

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Fri, 25 Apr 2008 09:02:31 GMT

I also implemented GetDataHere in Part 3.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

gcadmes — Sat, 26 Apr 2008 03:18:28 GMT

Great! Thank you!

In the SwfDataObjectExtensions.cs, when trying to SetDragImage(this IDataObject dataObject, Image image, System.Drawing.Point cursorOffset), in the first try/catch, the DeleteObject(hbmp) throws an EntryPointNotFoundException.

Also, I had to comment out AllowDropDescription() as I am running this code on XP SP2.

Any ideas will be greatly appreicated, and the code samples in your blog are equally appreciated.

Cheers,

Greg

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

gcadmes — Sat, 26 Apr 2008 03:50:05 GMT

I just discovered that the project I am working on must target the 2.0 Framework. After compiling the main core lib (DragDropLib) targeting the 2.0 Framework, there were several WPF compiler errors and warnings.

Unfortunately, I don’t think I can utilize your library after all; unless of course I painstakingly modify the code to work for 2.0. Do you suppose that would be a huge undertaking? I think the error count was around 100 or so.

Thanks again

Greg

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Sun, 27 Apr 2008 10:22:08 GMT

Refreshing the code to work with .NET 2.0 should be a fairly simple task. For the most part, you can work with only the System.Windows.Forms version of the code, so don't reference the WPF code. After that, you should see errors complaining about the .NET 3.5 extension method syntax (using "this" keyword on first parameter of static methods). Just remove "this", then fix all the "method doesn't exist for class" errors that remain to point to the static methods.

As for the DeleteObject problem, that seems strange. DeleteObject has been around since Windows 95/NT. You may want to investigate which GDI dll the function entry is referenced in, then use depends.exe (Dependency Walker) to verify the entry point exists in it.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Nishita — Tue, 03 Jun 2008 21:40:07 GMT

I am fairly new to Winforms and .NET. I have a winforms application in which there is a toolbox from which user selects which items to drag and drop on the control. Everytime i drag an item from the toolbox on the control i want to show the image of the toolbox item so that the user can drop the item within the printable bounds of the paper. What sections of your code will i be using ? Do i need to implement the COM interfaces ?

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Farhan — Mon, 07 Jul 2008 16:23:27 GMT

Hi,

A nice piece of code. I tried out the code.

I have a custom control derived from a panel being used as a thumbnail. The thumbnails are generated dynamically. So a common event handler for all controls generated. I am using the panel.DrawToBitmap() function to generatethe drag drop image resembling the thumbnail itself. But the code works only for the last added thumbnail control and not all the controls.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

James — Fri, 11 Jul 2008 19:34:10 GMT

Don't supose you have a C++ 2008 version of this?

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Kirk — Wed, 27 Aug 2008 02:15:20 GMT

I've got the drag descriptions working with a WinForms TreeView, but there's one minor thing I can't seem to sort out. As I drag over nodes that can accept a drop (DragDropEffects == Move or Copy), I properly see the drag description I set (based on the target node name). However, when I then move over another node in the tree that can't accept a drop (DragDropEffects == None), I do see the proper drag image but the drop description text box is still visible, albeit fairly small and empty. I was expecting only the drag image to appear -- not an empty drop description text box. I have a screen capture, but I don't see a way to attach that here. Any advice?

Thanks in advance.

-kirk

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Diego — Sun, 02 Nov 2008 21:06:11 GMT

Hello!, i have a problem and i think you could help me. I'm working with drag drops functions because i need to do a DROP into other windows app. My app knows the destination window, and i want to send a WM_DROPFILES message only to that window. I don't want a user doing the drag&drop, i want my app doing the task. I'm trying tu use postmessage, but it's doesn't work. can you help me with this?. thanks!

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Scott — Thu, 15 Jan 2009 23:27:14 GMT

I have been unable to track down wheat appears to be a bug in this. I have used your sample as a guide for a WPF application I am working on. I have set AllowDrop=True on my app's window, and added the DragOver, Enter, Leave, Drop overrides to the code behind, exactly as in your sample (in fact this bug happens in your sample as well).

If I drag an email message from Outlook over my app, it sets the drag drop effects to none, and it never changes. These two messages are continually output into the app's debug screen....

A first chance exception of type 'System.Runtime.InteropServices.COMException' occurred in PresentationCore.dll

A first chance exception of type 'System.Runtime.InteropServices.COMException' occurred in InterfaceUtilities.dll

The error itself is occuring in WpfDropTargetHelperExtensions.cs file in the DragEnter() method at the

dropHelper.DragEnter(windowHandle, (ComIDataObject)data, ref pt, (int)effect);

line.

If I remove the OnDrag-X overrides in the window's code behind, then the error does not occur, however then the drag adorner becomes somewhat unpredicatable when drop or leave occurs.

All I can figure is it may have something to do with the fact that there are no adorners when you drag from Outlook, causing the call to freak out? I have not yet been able to come up with a fix for it though.

Any ideas?

Thanks,

Scott

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Scott — Fri, 16 Jan 2009 17:23:38 GMT

When dragging an Outlook message over your sample form, a series of exception messages are spit out into the debug output window...

A first chance exception of type 'System.Runtime.InteropServices.COMException' occurred in PresentationCore.dll

A first chance exception of type 'System.Runtime.InteropServices.COMException' occurred in WpfDataObjectExtensions.dll

I was able to track down the exact message of the exception to "Invalid FORMATETC structure (Exception from HRESULT: 0x80040064(DV_E_FORMATETC))". It is erroring during the calls being made in the window drag drop overrides. The problem I have found with this in my application with this is that once this happens, drag and drop operations are not allowed from that point forward, even though I have controls that will accept this drop type.

So far I have not been able to solve this, other than to do a check on GetDataPresent("FileGroupDescriptor") and bypass the shell drag drop altogether if it's the data format.

Do you have any suggestions to avoid this error, or allow the library to more gracefully handle this situation?

Thanks,

Scott

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Scott — Fri, 16 Jan 2009 17:50:15 GMT

Further to my previous comment about dragging Outlook messages, I have noticed the same behavior when dragging text over the sample form. Just to add to it, as long as the textbox that accepts text is the first textbox the mouse goes after entering the form, it will still allow drop. However, if either the HTML or File textboxes are dragged over first, then the text textbox will not accept drops.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

folken — Thu, 05 Feb 2009 17:33:45 GMT

You were asking about why an alpha channel of 0 goes to black, but anything else works just fine. I don't know the answer, but venturing a guess I say it's probably a divide by 0 problem buried way down in windows.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Girly — Fri, 06 Feb 2009 16:40:49 GMT

How do I use this great preveiw when I want to pass my own custom data in the DataObject? If I try to use SetData I get: "Cannot SetData on a frozen OLE data object." The OLE data object is the custom dataobject. Supporting preview for drag from windows is great but I would like to support my own formats as well and pass data around.

I'm also struggeling with the position of the drag icon in my WPF application. But hopefully a little bit more testing will solve that.

Thanks!

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Thu, 19 Feb 2009 00:21:43 GMT

Nishita, the easiest thing for you would be to take a look at the SWF example from Part 3. If you are going with your own implementation, using this post as a guide, you'll need to implement the COM interface, and then learn to use the system IDragSourceHelper and IDropTargetHelper. Otherwise, just drop DragDropLib into your project (or compile and reference the appropriate DragDropLib.dll) and use it like the example uses it.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Thu, 19 Feb 2009 00:24:44 GMT

Farhan, you have all the control when creating the drag image. I tried to supply some helpers to make it easy, you may just need to pull it apart and figure out how to generate the bitmap as desired.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Thu, 19 Feb 2009 00:35:48 GMT

James, sorry, no, I don't have a C++ version of this.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Thu, 19 Feb 2009 00:36:53 GMT

Kirk, I think I saw that bug in the past. Did you ever resolve it? I have not.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Thu, 19 Feb 2009 00:37:41 GMT

Diego, sorry, I'm not your man for that issue.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Thu, 19 Feb 2009 00:41:03 GMT

Girly, you need to use SetDataEx, which is implemented as an extension methods to the appropriate DataObjects. This is a result of us providing the DataObject with a custom implementation. This is explained pretty thoroughly in Part 3.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Karin — Mon, 30 Mar 2009 11:10:05 GMT

I have a similar issue as did Scott, with a Invalid FORMATETC structure (Exception from HRESULT: 0x80040064 (DV_E_FORMATETC)) in IDropTargetHelper.DragEnter. It occurs when there is a standard drag and drop (not using the library) with text data. Such as this: System.Windows.DragDrop.DoDragDrop((ListView)sender, lc.Text, DragDropEffects.Copy);

This results in that I can not drop the text. I can catch the exception and bypass it but it does not seem right that I should get the exception.

It's a bit strange since dragging from an input field do work (the built in support in the control). But when I do it in code I get the exception.

Scott did you solve this?

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Tue, 31 Mar 2009 22:56:38 GMT

Karin, I'll see if I can reproduce your error and get back to you.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Rob — Tue, 23 Jun 2009 15:51:52 GMT

Scott, Karin:

I think that solution for this "Invalid FORMATC" problem is testing presence of DragImageBits data

if (e.Data.GetDataPresent("DragImageBits"))

DropTargetHelper.DragEnter(sender as Control, e.Data, new Point(e.X, e.Y), e.Effect);

It works for me. Can you confirm this Adam?

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Wed, 24 Jun 2009 16:43:34 GMT

Thanks, Rob. I hadn't gotten to this, but that sounds right. You should only call DropTargetHelper.DragEnter if the DragImageBits are present. I'm surprised the shell's implementation of IDropTargetHelper doesn't play nicer, but this check could potentially be added to the DropTargetHelper.DragEnter method wrapper.

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

Thierry — Sun, 22 Nov 2009 22:51:44 GMT

Hi,

We store various files in our database and I have a grid in my application in which I want to drag one or more records to windows explorer but only if the target is windows explorer, I would like to have a way for my application to know that the operation was successful and then only start extracting files from my database (when the drop event actually occured in explorer) and start copying them to the specific location where the "records" were dropped in the specific windows explorer.

I thought I could maybe put a dummy file in the DoDragDrop event and when the event is returned, delete it and start extracting the files but right now I have no way of knowing a) if it was a successful target and b) what is the path of the windows explorer it was dropped on?

Is this possible? Do you have any pointers?

Thanks.

Thierry

re: Shell Style Drag and Drop in .NET (WPF and WinForms)

adamroot — Mon, 23 Nov 2009 15:33:28 GMT

Thierry, I'm not sure actually. Usually, it is the target that decides whether to accept the dragged data.