Preventing Nested Drag and Drop in NavigationView Pages

Product Version	Product	Author
2025.2.520	NavigationView for WinForms	Dinko Krastev

Description

By default, the RadNavigationView control allows you to reorder the navigation view items according to your preferences. The drag-drop behavior of the RadNavigationView control is achieved by the RadPageViewDragDropService, which can be accessed by the RadNavigationView1.NavigationViewElement.ItemDragService property. If customization is required, we will need to create a custom class that derives from RadPageViewDragDropService and override the methods of the drag-drop service.

In the following scenario, the drag-drop should be performed on the first level only, thus disabling the option to have nested drag-drop. Also, the footer item should not be draggable.

Solution

To achieve this, create a custom drag-and-drop service and override specific methods. Follow these steps:

1. Prevent Nested Dragging and Dropping:
   Implement a custom class that derives from RadPageViewDragDropService. Override the CanDragOver method to restrict drop positions and prevent nested pages.

public class CustomDragDropService : RadPageViewDragDropService
{
    public CustomDragDropService(RadPageViewElement owner) : base(owner)
    {
    }

    protected override bool CanDragOver(RadPageViewItem pageViewItem)
    {
        if (!(pageViewItem is RadPageViewNavigationViewItem radPageViewNavigationViewItem))
        {
            return true;
        }

        if (!radPageViewNavigationViewItem.Enabled || !radPageViewNavigationViewItem.AllowDrop)
        {
            return false;
        }

        if (radPageViewNavigationViewItem.PinPosition == NavigationViewItemPinPosition.Footer)
        {
            return false;
        }

        DropPosition dropPosition = GetDropPosition(radPageViewNavigationViewItem, base.DropLocation);
        if (dropPosition == DropPosition.AsChildNode)
        {
            return false;
        }

        return base.CanDragOver(pageViewItem);
    }

    protected internal virtual DropPosition GetDropPosition(RadPageViewNavigationViewItem radPageViewNavigationViewItem, Point dropLocation)
    {
        int num = radPageViewNavigationViewItem.Size.Height / 3;
        int y = dropLocation.Y;
        if (y < num)
        {
            return DropPosition.BeforeNode;
        }

        if (y >= num && y <= num * 2)
        {
            return DropPosition.AsChildNode;
        }
        return DropPosition.AfterNode;
    }
}

1. Disable Dragging for Footer Page:
   Override the OnPreviewDragStart method to check the PinPosition property. Cancel the drag operation for the footer page.

protected override void OnPreviewDragStart(PreviewDragStartEventArgs e)
{
    var radPageViewNavigationViewItem = e.DragInstance as RadPageViewNavigationViewItem;
    if (radPageViewNavigationViewItem != null)
    {
        if (radPageViewNavigationViewItem.PinPosition == NavigationViewItemPinPosition.Footer)
        {
            e.CanStart = false;
        }
    }
    base.OnPreviewDragStart(e);
}

1. Assign Custom Drag-and-Drop Service:
   Set the custom service to the RadNavigationView control.

radNavigationView1.NavigationViewElement.ItemDragService = new CustomDragDropService(radNavigationView1.NavigationViewElement);

See Also

• RadNavigationView Overview Documentation
• RadPageViewDragDropService API Reference