Don't drag when selecting text with mouse

[Erik]

I have a RadListBox with DragDropBehavior, the RadListBox itemtemplates contain a textbox. I want the text in the textbox to be selectable using the mouse, but when I drag to select text, the item is dragged instead. Is it possible to disable drag within a control in an itemtemplate in a draggable RadListBox? I tried setting telerik:DragDropManager.AllowCapturedDrag="False" and telerik:DragDropManager.AllowDrag="False" on the textbox but that doesn't help.

Here's my little test project:

using System.Collections.ObjectModel;

namespace ListBoxTest
{
    public partial class MainWindow
    {
        public MainWindow()
        {
            InitializeComponent();

            DataContext = this;

            MyCollection = new ObservableCollection<string> { "test text 1", "test text 2", "test text 3", "test text 4", "test text 5", "test text 6" };
        }

        public ObservableCollection<string> MyCollection { get; private set; }
    }
}

<Window
    x:Class="ListBoxTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
    Title="MainWindow" Height="500" Width="525">
    <telerik:RadListBox
        ItemsSource="{Binding MyCollection}">
        <telerik:RadListBox.ItemTemplate>
            <DataTemplate>
                <Grid Height="50" Width="100" Background="LightBlue" telerik:DragDropManager.AllowCapturedDrag="True">
                    <TextBox
                        Text="{Binding .}"
                        VerticalAlignment="Center"
                        HorizontalAlignment="Center"
                        telerik:DragDropManager.AllowCapturedDrag="False"
                        telerik:DragDropManager.AllowDrag="False"/>
                </Grid>
            </DataTemplate>
        </telerik:RadListBox.ItemTemplate>
        <telerik:RadListBox.DragDropBehavior>
            <telerik:ListBoxDragDropBehavior />
        </telerik:RadListBox.DragDropBehavior>
    </telerik:RadListBox>
</Window>

[George]

Hello,

This behavior is expected because the RadListBoxItem container has AllowCapturedDrag set to true. In order to workaround the problem, I would suggest to remove the capture drag on TextBox_PreviewMouseLeftButtonDown handler and return it back in the TextBox_MouseLeave handler. Please, refer to the attached project and let me know if this helps.

Kind regards,
George
the Telerik team

[Erik]

Thanks that works great!

I created an attached behavior based on your code, and added some code to prevent dragged text from having a the same template as the listboxitems:

public class NoDragBehavior : Behavior<FrameworkElement>
    {
        private FrameworkElement Element
        {
            get { return AssociatedObject; }
        }

        public DataTemplate DragDataTemplate
        {
            get { return (DataTemplate)GetValue(DragDataTemplateProperty); }
            set { SetValue(DragDataTemplateProperty, value); }
        }

        public static readonly DependencyProperty DragDataTemplateProperty = DependencyProperty.Register
        (
            "DragDataTemplate",
            typeof(DataTemplate),
            typeof(NoDragBehavior),
            null
        );

        protected override void OnAttached()
        {
            base.OnAttached();

            Element.PreviewMouseLeftButtonDown += ElementOnPreviewMouseLeftButtonDown;
            Element.MouseLeave += ElementMouseLeave;
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();

            Element.PreviewMouseLeftButtonDown -= ElementOnPreviewMouseLeftButtonDown;
            Element.MouseLeave -= ElementMouseLeave;
        }

        private static void ElementOnPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs mouseButtonEventArgs)
        {
            var listboxItem = (sender as FrameworkElement).ParentOfType<RadListBoxItem>();
            if (listboxItem == null) return;

            DragDropManager.SetAllowCapturedDrag(listboxItem, false);
            var listbox = listboxItem.ParentOfType<RadListBox>();
            listbox.DragVisualProvider = new EmptyDragVisualProvider();
        }

        private void ElementMouseLeave(object sender, MouseEventArgs e)
        {
            var listboxItem = (sender as FrameworkElement).ParentOfType<RadListBoxItem>();
            if (listboxItem == null) return;

            DragDropManager.SetAllowCapturedDrag(listboxItem, true);
            var listbox = listboxItem.ParentOfType<RadListBox>();
            listbox.DragVisualProvider = new DragVisualProvider { DraggedItemTemplate = DragDataTemplate };
        }
    }

[Leland]

Is this still the preferred way to handle this scenario?

[Vladimir Stoyanov]

Hello Leland,

Indeed the demonstrated in this thread approach is the way to go to achieve the custom behavior in question. I do hope that such an approach is suitable for your scenario.

That said, if it is not, or you are having troubles with the implementation, feel free to open a new support ticket and describe your scenario. 

Regards,
Vladimir Stoyanov
Progress Telerik