Prevent Automatic Horizontal Scroll in TreeView

Question

Whenever a node is selected in my treeview, it automatically does a horizontal scroll to that item. Is there a way to disable this?

Answer 1

I had a similar problem. I needed to prevent horizontal scroll but preserve vertical scroll. My solution is to handle OnRequestBringIntoView method as I want it to behave. I created a ResourceDictionary for a TreeViewItem and added EventSetters for OnSelected and OnRequestBringIntoView methods.

MyResourceDictionary.xaml

MyResourceDictionary.xaml.cs

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;

namespace Resources
{
    partial class MyResourceDictionary:ResourceDictionary
    {
        public MyResourceDictionary()
        {
            InitializeComponent();
        }

        private void OnRequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
        {
            e.Handled = true; //prevent event bubbling
            var item = (TreeViewItem)sender;
            TreeView tree = GetParentTree(item) as TreeView;
            if(tree!=null)
            {
                var scrollViewer = tree.Template.FindName("_tv_scrollviewer_", tree) as ScrollViewer;
                if (scrollViewer != null)
                {
                    scrollViewer.ScrollToLeftEnd();//prevent horizontal scroll
                    Point relativePoint = item.TransformToAncestor(tree).Transform(new Point(0, 0));//get position of a selected item 
                    if (relativePoint.Y <= scrollViewer.ContentVerticalOffset) return;//do no scroll if we select inside one 'scroll screen'
                    scrollViewer.ScrollToVerticalOffset(relativePoint.Y);//scroll to Y of a selected item
                }
            }
        }

        private DependencyObject GetParentTree(DependencyObject item)
        {
            var target = VisualTreeHelper.GetParent(item);
            return target as TreeView != null ? target : GetParentTree(target);
        }

        private void OnSelected(object sender, RoutedEventArgs e) //handle programmatically selected items
        {
            var item = (TreeViewItem)sender;
            item.BringIntoView();
            e.Handled = true;
        }
    }
}