[Solved] TreeView dragcue

[Kelley Wong]

when i use silverlight 4,the dragcue works well
now i upgrade to silverlight 5 , it displays abnormally
i create a test project ,and the code as follows

<UserControl x:Class="RadControlsSilverlightApp1.MainPage"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
             mc:Ignorable="d"
             d:DesignWidth="640"
             d:DesignHeight="480">

    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition Width="2*" />
        </Grid.ColumnDefinitions>

        <telerik:RadTreeView x:Name="countryTree">
            <telerik:RadTreeViewItem IsExpanded="True"
                                     Header="Country">
                <telerik:RadTreeViewItem Header="Russia" />
                <telerik:RadTreeViewItem Header="Czech Republic" />
                <telerik:RadTreeViewItem Header="Poland" />
                <telerik:RadTreeViewItem Header="Greece" />
                <telerik:RadTreeViewItem Header="Germany" />
                <telerik:RadTreeViewItem Header="Portugal" />
                <telerik:RadTreeViewItem Header="Denmark" />
                <telerik:RadTreeViewItem Header="Netherlands" />
                <telerik:RadTreeViewItem Header="Spain" />
                <telerik:RadTreeViewItem Header="Croatia" />
                <telerik:RadTreeViewItem Header="Italy" />
                <telerik:RadTreeViewItem Header="Ireland" />
                <telerik:RadTreeViewItem Header="Ukraine" />
                <telerik:RadTreeViewItem Header="England" />
                <telerik:RadTreeViewItem Header="France" />
                <telerik:RadTreeViewItem Header="Sweden" />

            </telerik:RadTreeViewItem>
        </telerik:RadTreeView>

        <Canvas Grid.Column="1"
                x:Name="canvas" />
    </Grid>

</UserControl>

using System.Windows.Controls;
using Telerik.Windows.Controls.DragDrop;

namespace RadControlsSilverlightApp1
{
    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();

            RadDragAndDropManager.AddDropInfoHandler(canvas, OnDropInfo);
            RadDragAndDropManager.AddDropQueryHandler(canvas, OnDropQuery);

            RadDragAndDropManager.SetAllowDrop(canvas, true);

            RadDragAndDropManager.AddDragInfoHandler(countryTree, OnDragInfo);
            RadDragAndDropManager.AddDragQueryHandler(countryTree, OnDragQuery);
            RadDragAndDropManager.SetAllowDrag(countryTree, true);

        }

        private void OnDropInfo(object sender, DragDropEventArgs e)
        {
            var droppablePanel = e.Options.Destination;
            if (e.Options.Status == DragStatus.DropComplete && droppablePanel is Canvas)
            {

            }
        }

        private void OnDropQuery(object sender, DragDropQueryEventArgs e)
        {
            var droppablePanel = e.Options.Destination;
            if (e.Options.Status == DragStatus.DropDestinationQuery && droppablePanel is Canvas)
            {
                e.QueryResult = true;
                e.Handled = true;
            }
        }

        private void OnDragInfo(object sender, DragDropEventArgs e)
        {
            if (e.Options.Status == DragStatus.DragComplete)
            {

            }
        }

        private void OnDragQuery(object sender, DragDropQueryEventArgs e)
        {
            if (e.Options.Status == DragStatus.DragQuery)
            {
                #region Silverlight 5
                if (e.Options.Source is Telerik.Windows.Controls.RadTreeView)
                {
                    Telerik.Windows.Controls.RadTreeView draggedTreeView = e.Options.Source as Telerik.Windows.Controls.RadTreeView;

                    if (draggedTreeView.SelectedItem != null)
                    {
                        Telerik.Windows.Controls.RadTreeViewItem draggedTreeViewItem = draggedTreeView.SelectedItem as Telerik.Windows.Controls.RadTreeViewItem;

                        if (draggedTreeViewItem != null)
                        {
                            e.Options.DragCue = draggedTreeViewItem.Header;
                        }
                    }
                }
                #endregion

                #region Silverlight 4
                else if (e.Options.Source is Telerik.Windows.Controls.RadTreeViewItem)
                {
                    Telerik.Windows.Controls.RadTreeViewItem draggedTreeViewItem = e.Options.Source as Telerik.Windows.Controls.RadTreeViewItem;
                    if (draggedTreeViewItem != null)
                    {
                        e.Options.DragCue = draggedTreeViewItem.Header;
                    }
                }
                #endregion
            }

            e.QueryResult = true;
            e.Handled = true;
        }

    }
}

[Petar Mladenov]

Hi Kelley,

 This is issue has nothing to do with Silverlight version rather than the RadTreeView/RadDragDropManager internal logic.. Actually the DND Manager somehow uses the position of the RadTreeView for the start position of the DragCue. Do you need to set  AllowDrag on RadTreeView  ? I made the following changes to your code :
1) No need to set allow drag of the treeview. You always drag treeviewitems.

//RadDragAndDropManager.SetAllowDrag(countryTree, true);

2)Instead, set allow drag to every item

private void countryTree_ItemPrepared(object sender, RadTreeViewItemPreparedEventArgs e)
        {
            RadDragAndDropManager.SetAllowDrag(e.PreparedItem, true);
        }

3)The source is now always a radtreeviewitem:

private void OnDragQuery(object sender, DragDropQueryEventArgs e)
       {
           if (e.Options.Status == DragStatus.DragQuery)
           {
               if (e.Options.Source is Telerik.Windows.Controls.RadTreeViewItem)
               {
                   Telerik.Windows.Controls.RadTreeViewItem draggedTreeViewItem = e.Options.Source as Telerik.Windows.Controls.RadTreeViewItem;
                   if (draggedTreeViewItem != null)
                   {
                       e.Options.DragCue = draggedTreeViewItem.Header;
                   }
               }
           }
           e.QueryResult = true;
           e.Handled = true;
       }

Hope this re-factoring is suitable for you.
Regards,
Petar Mladenov
the Telerik team