Dragenter not firing.

Question

_{Monday, October 23, 2017 5:40 PM}

I cant get dragenter to fire.

The dragdrop routine works if I drag text from another app.

I am trying to drag data from a treeview into form1.

The treeview is inside a grid.

            this.AllowDrop = true;

            
            tbar2.DragEnter += new System.Windows.DragEventHandler(treeView1_DragEnter);
            tbar2.DragOver +=  new System.Windows.DragEventHandler(treeView1_DragOver);

            this.Drop += new System.Windows.DragEventHandler(treeView1_DragDrop);

            








        // Set the target drop effect to the effect 
        // specified in the ItemDrag event handler.
        private void treeView1_DragEnter(object sender, System.Windows.DragEventArgs e)
        {
           

            e.Effects = System.Windows.DragDropEffects.Copy;

            //            if (e.Data.GetDataPresent(System.Windows.DataFormats.Text))
            //              e.Effects = System.Windows.DragDropEffects.Copy;


          

            System.Windows.MessageBox.Show("11111111111111111111111111111111");
        }


        // Set the target drop effect to the effect 
        // specified in the ItemDrag event handler.
        private void treeView1_DragOver(object sender, System.Windows.DragEventArgs e)
        {
            e.Effects = System.Windows.DragDropEffects.Copy;

            

            System.Windows.MessageBox.Show("222222222222222222222222222222222");
        }




        private void treeView1_DragDrop(object sender, System.Windows.DragEventArgs e)
        {
            // Retrieve the node that was dragged.
            
           
            String tr;
            tr = e.Data.ToString();
            System.Windows.MessageBox.Show(tr);

            System.Windows.MessageBox.Show("33333333333333333333333333333333333");
        }


        

n.Wright

All replies (5)

_{Monday, October 23, 2017 11:14 PM ✅Answered}

I had to add the enclosed code to get it to work.

I also have a C++ versionof this program and that didn't need the extra code.

        private void ListBox_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {


            object data = GetDataFromListBox(tbar2, e.GetPosition(tbar2));

            if (data != null)
            {
                DragDrop.DoDragDrop(tbar2, data, System.Windows.DragDropEffects.Move);
            }
        }



        private static object GetDataFromListBox(System.Windows.Controls.TreeView source, Point point)
        {
            UIElement element = source.InputHitTest(point) as UIElement;
            if (element != null)
            {
                object data = DependencyProperty.UnsetValue;
                while (data == DependencyProperty.UnsetValue)
                {
                    data = source.ItemContainerGenerator.ItemFromContainer(element);

                    if (data == DependencyProperty.UnsetValue)
                    {
                        element = VisualTreeHelper.GetParent(element) as UIElement;
                    }

                    if (element == source)
                    {
                        return null;
                    }
                }

                if (data != DependencyProperty.UnsetValue)
                {
                    return data;
                }
            }

            return null;
        }

n.Wright

_{Tuesday, October 24, 2017 3:12 AM ✅Answered}

It is a C# WPF program.

It is using a grid for the user interface.

The problem has been fixed as above.

I think the C# drag and drop doesn't have the itemdrag like C++.

So I had to add a mouse preview event handler.

Once this was added the drag and drop started working.

n.Wright

_{Monday, October 23, 2017 6:59 PM}

I also have a textbox in the same grid and that does allow drag drop.

n.Wright

_{Monday, October 23, 2017 7:10 PM}

I also have a textbox in the same grid and that does allow drag drop.

n.Wright

Listbox and listview have the same problem.

n.Wright

_{Tuesday, October 24, 2017 3:09 AM}

Hello nigelwright7557,

What is the type of your project? Winform,Uwp,Wpf or others, please provide more details about your program  so that we can do further test with it.

Sincerely,

Neil Hu

MSDN Community Support
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