Why my WPF application has Drag & Drop disabled (even when AllowDrop is true)?

Question

My WPF application inhibits the Drop of files from Windows Explorer, showing a Stop-sign cursor.

I've tried setting the AllowDrop property (that of the UIElement ancestor) to true on the main window and contained controls, but no luck at all, no drag-drop events are fired.

Any ideas or suggestions to find the cause?

I cannot provide code because it's huge (a lot of custom wpf controls). I need some point of view or cue from which to face this problem, from where to start looking for the solution. — Néstor Sánchez A., Aug 03 '13 at 09:55
@GarryVass my App has the default trust level of a WPF desktop application. It is not an XBAP application for web deployment, so it has full trust I believe. — Néstor Sánchez A., Aug 05 '13 at 06:05

score 25 · Answer 1 · edited May 23 '17 at 12:17

25

Solved!

The problem was that executing my app thru VisualStudio (run/debug) prevented the interop with Windows' drag & drop mechanism. Running the App as stand-alone makes it work, but cannot debug interactively.

This answer helped a lot: Visual Studio 2010 WPF Project ran in debug or relase will not allow drag and drop to any control

edited May 23 '17 at 12:17

Community

1
1

answered Aug 21 '13 at 02:38

Néstor Sánchez A.

3,848
10
44
68

1

At least it's possible to attach to the process, and hit breakpoints afterward. – Matthieu Mar 15 '22 at 14:08

score 19 · Answer 2 · answered Oct 04 '19 at 12:30

19

In my case it was running Visual Studio as Administrator on Windows 10. The UAC prevented the drag/drop. When I ran VS without elevating drag/drop started working in debug mode.

answered Oct 04 '19 at 12:30

stambikk

1,175
12
23

1

stambikk, you just saved me hours! – David Ehnis Dec 20 '19 at 14:18
This is really strange behavior but you're right. Thanks for finding this. – Smitty-Werben-Jager-Manjenson Apr 15 '21 at 16:59
1

It's because the user running your application in Debug mode is a different user than the one who opened the Windows Explorer window. Same reason your debug version of an application won't see networked drives. I stumbled on this after 2+ hours of Google searching. It finally makes sense. – Paul Nov 09 '21 at 18:40
this was my issue too, thank you! – 3xGuy Oct 07 '22 at 08:35

score 7 · Answer 3 · answered Apr 26 '17 at 11:19

7

According to this: http://codeinreview.com/136/enabling-drag-and-drop-over-a-grid-in-wpf/ (Which I am happy to report works!)

All you need to do is add a background on the control that has to get the drop. This will enable hit testing and thus make the drop-feature work.

Note: The background can be transparent, you just have to set it.

answered Apr 26 '17 at 11:19

aliceraunsbaek

625
7
18

Of course, the reported problem occurs having a background (i.e. it was not a fancy backgroundless UI trying to reach a transparency effect). – Néstor Sánchez A. Apr 27 '17 at 22:04

Why my WPF application has Drag & Drop disabled (even when AllowDrop is true)?

3 Answers3

Linked