WPF Treeview Drag and Drop

Question

Hi All,
I faced an when using WPF Treeview Drag and Drop function. Firstly, I can achieve Drag and Drop in a general TreeViewItem. I followed this article in CodeProject: http://www.codeproject.com/Articles/55168/Drag-and-Drop-Feature-in-WPF-TreeView-Control
This scenario works for the TreeViewItem looks like below,
<TreeView x:Name="_countries" AllowDrop="True" MouseLeftButtonDown="OnTMouseDown">
<TreeViewItem Header="USA">
<TreeViewItem Header="New York"/>
<TreeViewItem Header="Canifonia"/>
<TreeViewItem Header="Sourth East">
<TreeViewItem Header="Houston"/>
<TreeViewItem Header="DAL"/>
<TreeViewItem Header="SAN"/>
</TreeViewItem>
</TreeViewItem>
<TreeViewItem Header="China">
<TreeViewItem Header="Beijing"/>
<TreeViewItem Header="Jiangsu">
<TreeViewItem Header="Nantong"/>
<TreeViewItem Header="Suzhou"/>
<TreeViewItem Header="Wuxi"/>
</TreeViewItem>
</TreeViewItem>
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<EventSetter Event="TreeViewItem.DragOver" Handler="OnTDragOver"/>
<EventSetter Event="TreeViewItem.Drop" Handler="OnTDrop"/>
<EventSetter Event="TreeViewItem.MouseMove" Handler="OnTMouseMove"/>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
My Question is if i custom the TreeView Item like:
<TreeView.ItemTemplate>
<HierarchicalDataTemplate DataType="{x:Type local:QuestionInfo}" ItemsSource="{Binding Infos}">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Path=Name}"/>
<TextBlock Text="{Binding Path=Score}"/>
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
1. How to achieve the Drag and Drop function?
2. Since the data is binding to TreeView, When i Drag and Drop item. I want to keep the same order in my data source. In other words, If i drag the third TreeView Item to the first item.
3. How to change the Drag and Drop animation?
Could you please do me a favor?
Thanks a lot.

Answer 1

Hello Ricky,
For question 1, "How to achieve the Drag and Drop function?"
I would recommend you read a blog from here:
http://wpftutorial.net/DragAndDrop.html?showallcomments
The important part of this code is the following line:
// Get the dragged ListViewItem
ListView listView = sender as ListView;
ListViewItem listViewItem =
FindAnchestor<ListViewItem>((DependencyObject)e.OriginalSource);
And the FindAnchestor is to find the parent of your selection:
// Helper to search up the VisualTree
private static T FindAnchestor<T>(DependencyObject current)
where T : DependencyObject
do
if( current is T )
return (T)current;
current = VisualTreeHelper.GetParent(current);
while (current != null);
return null;
Please consider the following scenario, if you have a textbox in a canvas, if you want to drag and drop your textbox, you are using the function about to search for it parent object, the canvas and then you are moving that canvas. In this way we can drag
and drop a item which may contains the textbox you mentioned.
A complete sample can be checked from a great blog below:
http://openszone.com/solution/how-to-accomplish-drag-and-drop-wpf-treeviewitem
And for the question about the Drag and Drop animation, do you mean you want to "create a preview effect for the operation"
If so, try this blog：http://blogs.msdn.com/b/marcelolr/archive/2006/03/03/showing-drag-drop-feedback-on-the-wpf-adorner-layer.aspx
The second question "data source", I think we can talk about it if you can share how you defined your datasource. That is more reasonable then just guess how your source will be filled into treeview.
Anyway, I would recommend you check Flankin's blog for some details about this.
Best regards,
Barry
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