Accessing DropPosition in OnDropQuery (Drag'n'drop)?

[Anders]

Hi Telerik,

I can't seem to find the DropPosition when determining wheter a drop is allowed? Am I overlooking something? I can see the relative position and I guess I could calculate the relative position, but since the curson changes depending on drop position, I'm thinking the information is there somewhere...

Thnaks for any help,

Anders, Denmark

[Petar Mladenov]

Hello Anders,

 You can first access the destination ( TreeViewItem  or TreeView) and get the position like so:

var item = e.Options.Destination as RadTreeViewItem;
            if (item.DropPosition != DropPosition.Inside)
                e.QueryResult = false;

Please let us know if this helps you or not. All the best,
Petar Mladenov
the Telerik team

[Anders]

Thank you - it works like a charm!

[Robert]

Hi,

The sample you gave is the same as the documentation and it works well.
However, how can I stop a "Group" node from being dropped inside another "Group" node?

Thank you for your time.

[Robert]

Ok, well I worked this out:

private void OnDropInsideTreeViewDropQuery(object sender, DragDropQueryEventArgs e)
{
//Drop Destination
var treeViewItem = e.Options.Destination as RadTreeViewItem;
//Node being dragged
object selectedTreeItem = ((RadTreeViewItem)e.OriginalSource).Item;

//Check if node being dragged is top node
if (selectedTreeItem is ParksGroupDataStruct)
{
e.QueryResult = false;
}
//If not top node being dragged then only allow drop inside
else if (treeViewItem.DropPosition != DropPosition.Inside)
{
e.QueryResult = false;
}
}

Not sure if this is the best way to do it, but it works. If there's any better advice then I'm all ears (or eyes in this case).

Now I need to figure out the null exception being thrown if item is being dragged into white space of TreeView.

[Robert]

Here's the code to disable drop in white space to cancel out the null exception thrown.

private void OnDropInsideTreeViewDropQuery(object sender, DragDropQueryEventArgs e)
        {
            //Drop Destination
            var destinationTreeViewItem = e.Options.Destination as RadTreeViewItem;
            //Node being dragged
            object selectedTreeItem = ((RadTreeViewItem)e.OriginalSource).Item;

            //Check drop destination isn't null (white space)
            if (destinationTreeViewItem == null)
            {
                e.QueryResult = false;
            }
            //Check if node being dragged is top node
            else if (selectedTreeItem is ParksGroupDataStruct)
            {
                e.QueryResult = false;
            }
            //If not top node being dragged then only allow drop inside
            else if (destinationTreeViewItem.DropPosition != DropPosition.Inside)
            {
                e.QueryResult = false;
            }
        }

[Tina Stancheva]

Hi Robert,

I am glad you found a solution for your scenario. Handling the OnDropQuery event is the right approach for your case, but should you encounter any issues with it or you need our assistance, please let us know.

Regards,
Tina Stancheva
the Telerik team