Drag and Drop in a ListView

[Tom Bean]

I wrote an C# application that uses drag and drop to copy the contents of
one ListViewItem to another. I call DoDragDrop() in the ItemDrag event
handler, however, the ItemDrag event is being fired when an item in the
ListView is clicked to select it instead of being fired when the item is
dragged.

This is causing a problem when users click on an item and move the moue
(after the mouse button has been released) because the app tries to perform
the drag and drop operation, copy, even though the item wasn't dragged to
another item before the mouse button was released.

I have tried implementing handlers for the MouseUpand QueryContinueDr ag
events to cancel the drag and drop if the mouse button is released over the
selected item. Neither event handler is hit before the mouse is moved off
the selected item.

I need to find a way to cancel the drag or even better to find out how to
prevent ItemDrag from firing when the ListViewitem is clicked on to select
it.

Has anyone got any suggestions about how to solve this problem?

Thanks,
Tom

[Linda Liu[MSFT]]

Hi Tom,

Thank you for your prompt reply!

I performed a test on your new finding. I add some lines of code which will
take several seconds to complete in the SelectedIndexCh anged event handler
as follows:

void listView1_Selec tedIndexChanged (object sender, EventArgs e)
{
Console.WriteLi ne("begin: selected index changed");
int j = 0;
for (int i = 0; i < 10000; i++)
{
for (int k = 0; k < 10000; k++)
{
j += i;
}
}
Console.WriteLi ne("end: selected index changed");
}

void listView1_ItemD rag(object sender, ItemDragEventAr gs e)
{
Console.WriteLi ne("item drag");
}

Then I run my test application by pressing F5 and select and drag one item
in the ListView. The result I get is that the string "item drag" is always
printed after the string "end: selected index changed" in the Output
window, which means the ItemDrag event handler is called only after the
SelectedIndexCh anged event handler is completed.

If you don't call the time-consuming method from within the
SelectedIndexCh anged event handler, does the problem disappear? If so, you
may have a try calling the Control.BeginIn voke method to execute a delegate
for the time-consuming method asynchronously.

Hope this helps.
If the problem is still not solved, please feel free to let me know.

Sincerely,
Linda Liu
Microsoft Online Community Support

Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
ms****@microsof t.com.

This posting is provided "AS IS" with no warranties, and confers no rights.

[Linda Liu[MSFT]]

Hi Tom,

Thank you for your prompt reply!

Is the problem solved now? If not, please feel free to let me know.

Thank you for using our MSDN Managed Newsgroup Support Service!

Sincerely,
Linda Liu
Microsoft Online Community Support

Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
ms****@microsof t.com.

This posting is provided "AS IS" with no warranties, and confers no rights.