Merge pull request #762 from telerik/new-kb-navigationview-drag-drop-customize-312a116756d346b88b2a193f90ede1c7

Added new kb article navigationview-drag-drop-customize

Author: nade7o

knowledge-base/navigationview-drag-drop-customize.md

@@ -0,0 +1,115 @@
+---
+title: Preventing Nested Drag and Drop in NavigationView Pages
+description: Learn how to prevent nested drag and drop and pin a footer page in the RadNavigationView for UI for WinForms.
+type: how-to
+page_title: How to Avoid Nested Drag and Pin Footer Page in RadNavigationView
+meta_title: How to Avoid Nested Drag and Pin Footer Page in RadNavigationView
+slug: navigationview-drag-drop-customize
+tags: navigationview, ui-for-winforms, drag-drop, footer, custom-drag-drop-service
+res_type: kb
+ticketid: 1691649
+---
+
+|Product Version|Product|Author|
+|----|----|----|
+|2025.2.520|NavigationView for WinForms|[Dinko Krastev](https://www.telerik.com/blogs/author/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.
+
+````C#
+
+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;
+    }
+}
+
+````
+
+2. **Disable Dragging for Footer Page:**  
+   Override the `OnPreviewDragStart` method to check the `PinPosition` property. Cancel the drag operation for the footer page.
+
+````C#
+
+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);
+}
+
+````
+
+3. **Assign Custom Drag-and-Drop Service:**  
+   Set the custom service to the RadNavigationView control.
+
+````C#
+
+radNavigationView1.NavigationViewElement.ItemDragService = new CustomDragDropService(radNavigationView1.NavigationViewElement);
+
+````
+
+## See Also
+
+* [RadNavigationView Overview Documentation](https://docs.telerik.com/devtools/winforms/controls/navigationview/overview)
+* [RadPageViewDragDropService API Reference](https://docs.telerik.com/devtools/winforms/api/html/T_Telerik_WinControls_UI_RadPageViewDragDropService.htm)