Changing the payload on OnDragOver

[danparker276]

I'm trying to migrate my legacy drag and drop, but I can't seem to change the text of the cue or payload or draggeditem template when I drag my item over the trashcan image.  I basically just want it to say 'Delete' when it can be dragged.

For example, I'm dragging an item and when I want to 

This is my old code:

        private void OnDropInfoTrash(object sender, DragDropEventArgs e)
        {
...
ApplicationInfo payload = e.Options.Payload as ApplicationInfo;

 

ContentControl cue = e.Options.DragCue as ContentControl;

ContentControl arrow = e.Options.ArrowCue as ContentControl;

if (e.Options.Status == DragStatus.DropPossible)

{

    ApplicationInfo api = new ApplicationInfo();

    api.recno = ((ApplicationInfo)cue.Content).recno;

    api.IconPath = "/TimeEntrySL;component/Icons/timeentrySM1.png";

    api.IconText = "Delete";

    cue.Content = api;

}
else ...

This is what I tried in my new code, but this doesn't seem to do anything on the drag over

     DragDropManager.AddDragOverHandler(imgTrash, OnDragOverTrash);

private void OnDragOverTrash(object sender, Telerik.Windows.DragDrop.DragEventArgs e)

{         

    IDragPayload payload = (IDragPayload)e.Data;

    ApplicationInfo aa = (ApplicationInfo)((IDragPayload)e.Data).GetData("DragData");

        aa.IconText = "Delete";

        e.Effects = DragDropEffects.All;

        payload.SetData("DragData", aa);

        payload.SetData("DropDetails", aa);

        e.Handled = true;

}

Is it possible to do this?

[Yoan]

Hello,

In order to achieve your goal, you need to save a reference to the DragVisual in the DragInitialize event and use it later on to modify it as you wish.

Hope this helps! 

Regards,
Yoan
Telerik

[danparker276]

I don't seem to get the result that I want, maybe I'm missing something.

It seems like I can change the text in OnGiveFeedback:
   DragDropManager.AddGiveFeedbackHandler(myListBox, OnGiveFeedback);

but, I it doesn't fire off an event if I do a feedbackhandler on the trash image.  
     DragDropManager.AddGiveFeedbackHandler(imgTrash, OnGiveFeedbackTrash);
So I guess this is only on the listbox.  (This doesn't hit my breakpoint when I drag the item over the trash image)


The dragover handler works, but it won't change my text:

 DragDropManager.AddDragOverHandler(imgTrash, OnDragOverTrash);
        private void OnDragOverTrash(object sender, Telerik.Windows.DragDrop.DragEventArgs e)
        {
        aaCurrent.IconText = "Delete"; //This is global
            dragVisualRef = new ContentControl { Content = aaCurrent, ContentTemplate = this.Resources["ApplicationDragTemplate"] as DataTemplate };

Maybe I'm missing something?

[Yoan]

Hello Dan,

You can check this online demo on how the ListBoxDragDropBehavior is implemented. The code determining the drop details as dragging over is inside OnDragOver method.

Regards,
Yoan
Telerik

[danparker276]

I've been trying to use that ondragOver method, but maybe it's over my head.

aaCurrent.IconText = "Delete";
var dropDetails = DragDropPayloadManager.GetDataFromObject(e.Data, "DropDetails") as DropIndicationDetails;
dropDetails.CurrentDraggedOverItem = aaCurrent;
dropDetails.CurrentDropPosition = Telerik.Windows.Controls.DropPosition.Inside;

e.Handled = true;

I tried this on the drag over, but it doesn't add the text when I drag over.  It's like I need to do some sort of refresh on the dragvisual.
my aaCurent item is now global, so the next time I try to drag something it shows "Delete" because I only set the text here.  So I know it's being set.
Again, maybe this is over my head and I can't spend a few days trying to figure this out from that example.

[Nick]

Hi,

You need to change the Content of your current DragVisual, rather that assigning a new one. The problem is that the Visual cannot be replaced as a whole while dragging. You need to set the Content to the updated value in order to get the changes.

Hope this helps! 

Regards,
Nik
Telerik

[danparker276]

Sorry it just isn't working for me even if I make every thing global

aaCurrent.IconText = "Delete";
ContentControl ccl = (ContentControl)dragVisualRef;
ccl.Content = aaCurrent;
ccl.ContentTemplate = this.Resources["ApplicationDragTemplateDel"] as DataTemplate;
dragVisualRef = ccl;

I even tried using a converter on the template.  Nothing changes it.

How do I get my current dragVisual from this besides making it global?
  private void OnDragOverTrash(object sender, Telerik.Windows.DragDrop.DragEventArgs e)

[Nick]

Hi Dan,

You shouldn't change the dragVisual reference itself. The change of the Visual in the DragOver handler should look something like: 

(this.dragVisualRef as ContentControl).Content = new Content

Hope this makes sense! 

Regards,
Nik
Telerik

[danparker276]

Success!!  Thank you.  It's very easy now actually.

This below is all that was really needed.

public MyControl(){
   InitializeComponent();
 DragDropManager.AddDragInitializeHandler(listBoxTasks, OnDragInitialize);
      DragDropManager.AddGiveFeedbackHandler(listBoxTasks, OnGiveFeedback);
         DragDropManager.AddDragOverHandler(imgTrash, OnDragOverTrash);
    DragDropManager.AddDropHandler(imgTrash, OnTrashDrop);
}

        private void OnDragOverTrash(object sender, Telerik.Windows.DragDrop.DragEventArgs e)
        {
            (this.dragVisualRef as ContentControl).Content = new ApplicationInfo() { IconPath = "/MyApp;component/Icons/TaskImg.png", recno = aaCurrent.recno, IconText = "Delete" };
}

        private void OnDragInitialize(object sender, DragInitializeEventArgs args)
        {
          ...
            args.Data = payload;
            args.DragVisual = new ContentControl { Content = aaCurrent, ContentTemplate = this.Resources["ApplicationDragTemplate"] as DataTemplate };
            dragVisualRef = args.DragVisual;
        ...
        }
        private void OnGiveFeedback(object sender, Telerik.Windows.DragDrop.GiveFeedbackEventArgs args)
        {
            (this.dragVisualRef as ContentControl).Content = new ApplicationInfo() { IconPath = "/MyApp;component/Icons/TaskImg.png", recno = aaCurrent.recno, IconText = "" };

        }