diff -r 3145aadca3d2 -r 0c551e8818e0 External/Aga.Controls/Tree/TreeColumnCollection.cs
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/External/Aga.Controls/Tree/TreeColumnCollection.cs	Sun May 27 15:16:19 2012 +0000
@@ -0,0 +1,98 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Windows.Forms;
+
+namespace Aga.Controls.Tree
+{
+	internal class TreeColumnCollection : Collection<TreeColumn>
+	{
+		private TreeViewAdv _treeView;
+
+		public TreeColumnCollection(TreeViewAdv treeView)
+		{
+			_treeView = treeView;
+		}
+
+		protected override void InsertItem(int index, TreeColumn item)
+		{
+			base.InsertItem(index, item);
+			BindEvents(item);
+			_treeView.UpdateColumns();
+		}
+
+		protected override void RemoveItem(int index)
+		{
+			UnbindEvents(this[index]);
+			base.RemoveItem(index);
+			_treeView.UpdateColumns();
+		}
+
+		protected override void SetItem(int index, TreeColumn item)
+		{
+			UnbindEvents(this[index]);
+			base.SetItem(index, item);
+			item.Owner = this;
+			BindEvents(item);
+			_treeView.UpdateColumns();
+		}
+
+		protected override void ClearItems()
+		{
+			foreach (TreeColumn c in Items)
+				UnbindEvents(c);
+			Items.Clear();
+			_treeView.UpdateColumns();
+		}
+
+		private void BindEvents(TreeColumn item)
+		{
+			item.Owner = this;
+			item.HeaderChanged += HeaderChanged;
+			item.IsVisibleChanged += IsVisibleChanged;
+			item.WidthChanged += WidthChanged;
+			item.SortOrderChanged += SortOrderChanged;
+		}
+
+		private void UnbindEvents(TreeColumn item)
+		{
+			item.Owner = null;
+			item.HeaderChanged -= HeaderChanged;
+			item.IsVisibleChanged -= IsVisibleChanged;
+			item.WidthChanged -= WidthChanged;
+			item.SortOrderChanged -= SortOrderChanged;
+		}
+
+		void SortOrderChanged(object sender, EventArgs e)
+		{
+			TreeColumn changed = sender as TreeColumn;
+			//Only one column at a time can have a sort property set
+			if (changed.SortOrder != SortOrder.None)
+			{
+				foreach (TreeColumn col in this)
+				{
+					if (col != changed)
+						col.SortOrder = SortOrder.None;
+				}
+			}
+			_treeView.UpdateHeaders();
+		}
+
+		void WidthChanged(object sender, EventArgs e)
+		{
+			_treeView.ChangeColumnWidth(sender as TreeColumn);
+		}
+
+		void IsVisibleChanged(object sender, EventArgs e)
+		{
+			_treeView.FullUpdate();
+		}
+
+		void HeaderChanged(object sender, EventArgs e)
+		{
+			_treeView.UpdateView();
+		}
+	}
+}