Hi,

I am currently testing how to use Drag and Drop between two RadGridViews.

But I am experiencing bugs in Q1 2010 for SIlverlight!

Both GridViews have AllowDrag and AllowDrop set to true.

When I start dragging from one grid to the other using an RadDragAndDropManager.GenerateArrowCue() the arrow is showing ok when I am moving in the source grid. As soon as I approach the destination grid the arrow is not extending smoothly, it suddenly begins to multiply as soon as the mouse enters the target grid until I release the mouse button I have hundreds of arrows on the screen because the arrows are not deleted when I am in the target area! When the drag and drop cursor is outside a grid it works fine, as soon as it enters the destination grid: boom!

This behavior is shown in the second of the attached pictures.

The next bug is that I can start my drag and drop action while I am on a vertical or horizontal scrollbar! Usually when you click on a scrollbar you expect the slider to move in a certain direction or that you can drag the slider to a specific position. When I have drag and drop enabled on my gridviews it shows the drag and drop arrowcue when I am manipulating the scrollbar sliders! This behaviour is shown on the first attached picture.

The third bug is that the gridview is automatically selecting new items when I drag and drop.

Example: My Grid has SelectionMode="Extended" turned on to allow me to select more than one item. I select 5 items and start dragging them to another gridview. From time to time as I start dragging in the source gridview the source gridview ads additional items to my selected items (because I hovered over them) so that I end up dragging more items than I originally selected into the destination grid.

All of these problems don't seem to appear when I use a VisualCue.

Greets Janni

I had a similar ArrowCue-Problem, but it is not a "hefty bug", it is art :-)

You can reproduce the multiple arrows with your own SL-Demo "Tree to Grid Drag".
Add to the "OnOrderDragQuery"-Method after "e.Options.Payload = selectedItems"
the following line:

e.Options.ArrowCue = RadDragAndDropManager.GenerateArrowCue();

This will reproduce the problem. I have looked at your (Telerik) source code
to find out the cause.

Every RadDragAndDropManager.GenerateArrowCue() generates a new object.
Referring to your documentation this usually happens in the OnDragQuery
(like in your modified Demo) event handler.

In the source code (not of the demo, I mean the source code of the controls) you
find in RadDragAndDropManager.cs the method "PositionArrow()". In this method
every call adds the ArrowCue-Object to the Grid. The "If...Children.Contains..." condition
do not consider the fact, that almost on every call Options.ArrowCue is a new object.
I found a method  "ResetEverything" which removes only the current ArrowCue-object
from the grid, not all.

Workaround: Call RadDragAndDropManager.GenerateArrowCue() only once per complete
drag-and-drop operation.

The "second bug" Paul described (drag-and-drop-starting-on-scrollbar-slider.jpg) is
probably caused by the fact, that he must set the AllowDrag-Property to the GridViewRow,
not to the GridView.

The "third bug" he reported is indeed a problem (for me too), but I am not sure if it
is a normal behavior or a real bug.The default behavior of the grid in the
SelectionMode="Extended" is to select the hovered item. But in "Drag-State" this
behavior is not very desirable.

Kind regards,
Michael