CyberX8/Framework/UICore/ExtendedControls/TreeViewHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;

namespace MECF.Framework.UI.Core.ExtendedControls
{
    public class BindableSelectedItemBehavior : Behavior<TreeView>
    {
        #region SelectedItem Property

        public object SelectedItem
        {
            get { return (object)GetValue(SelectedItemProperty); }
            set { SetValue(SelectedItemProperty, value); }
        }

        public static readonly DependencyProperty SelectedItemProperty =
            DependencyProperty.Register("SelectedItem", typeof(object), typeof(BindableSelectedItemBehavior), new UIPropertyMetadata(null, OnSelectedItemChanged));

        private static void OnSelectedItemChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            var item = e.NewValue as TreeViewItem;
            if (item != null)
            {
                item.SetValue(TreeViewItem.IsSelectedProperty, true);
            }
        }

        #endregion

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

            this.AssociatedObject.SelectedItemChanged += OnTreeViewSelectedItemChanged;
        }

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

            if (this.AssociatedObject != null)
            {
                this.AssociatedObject.SelectedItemChanged -= OnTreeViewSelectedItemChanged;
            }
        }

        private void OnTreeViewSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
        {
            this.SelectedItem = e.NewValue;
        }
    }

    public class TreeViewHelper
    {
        private static Dictionary<DependencyObject, TreeViewSelectedItemBehavior> behaviors = new Dictionary<DependencyObject, TreeViewSelectedItemBehavior>();

        public static object GetSelectedItem(DependencyObject obj)
        {
            return (object)obj.GetValue(SelectedItemProperty);
        }

        public static void SetSelectedItem(DependencyObject obj, object value)
        {
            obj.SetValue(SelectedItemProperty, value);
        }

        // Using a DependencyProperty as the backing store for SelectedItem.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty SelectedItemProperty =
            DependencyProperty.RegisterAttached("SelectedItem", typeof(object), typeof(TreeViewHelper), new UIPropertyMetadata(null, SelectedItemChanged));

        private static void SelectedItemChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
        {
            if (!(obj is TreeView))
                return;

            if (!behaviors.ContainsKey(obj))
                behaviors.Add(obj, new TreeViewSelectedItemBehavior(obj as TreeView));

            TreeViewSelectedItemBehavior view = behaviors[obj];
            view.ChangeSelectedItem(e.NewValue);
        }

        private class TreeViewSelectedItemBehavior
        {
            TreeView view;
            public TreeViewSelectedItemBehavior(TreeView view)
            {
                this.view = view;
                view.SelectedItemChanged += (sender, e) => SetSelectedItem(view, e.NewValue);
            }

            internal void ChangeSelectedItem(object p)
            {
                TreeViewItem item = (TreeViewItem)view.ItemContainerGenerator.ContainerFromItem(p);
                item.IsSelected = true;
            }
        }
    }
}