diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj
index 60eb588371..e4593dfc48 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj
@@ -366,7 +366,6 @@
     <Compile Include="Xml\TrackedSegmentCollection.cs">
       <DependentUpon>AXmlParser.cs</DependentUpon>
     </Compile>
-    <Compile Include="Xml\ExtensionMethods.cs" />
     <Compile Include="Xml\FilteredCollection.cs" />
     <Compile Include="Xml\IAXmlVisitor.cs" />
     <Compile Include="Xml\MergedCollection.cs" />
diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Xml/AXmlContainer.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Xml/AXmlContainer.cs
index 641c8472ff..761acbc091 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Xml/AXmlContainer.cs
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Xml/AXmlContainer.cs
@@ -60,7 +60,7 @@ namespace ICSharpCode.AvalonEdit.Xml
 		/// <inheritdoc/>
 		public override IEnumerable<AXmlObject> GetSelfAndAllChildren()
 		{
-			return (new AXmlObject[] { this }).Flatten(
+			return NRefactory.Utils.TreeTraversal.PreOrder(this,
 				delegate(AXmlObject i) {
 					AXmlContainer container = i as AXmlContainer;
 					if (container != null)
diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Xml/ExtensionMethods.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Xml/ExtensionMethods.cs
deleted file mode 100644
index bc1de81bfc..0000000000
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Xml/ExtensionMethods.cs
+++ /dev/null
@@ -1,47 +0,0 @@
-// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
-// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
-
-using System;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.Collections.Specialized;
-using System.Diagnostics;
-using System.Linq;
-
-using ICSharpCode.AvalonEdit.Document;
-
-namespace ICSharpCode.AvalonEdit.Xml
-{
-	static class ExtensionMethods
-	{
-		// Copied from ICSharpCode.SharpDevelop.Dom.ExtensionMethods
-		/// <summary>
-		/// Converts a recursive data structure into a flat list.
-		/// </summary>
-		/// <param name="input">The root elements of the recursive data structure.</param>
-		/// <param name="recursion">The function that gets the children of an element.</param>
-		/// <returns>Iterator that enumerates the tree structure in preorder.</returns>
-		public static IEnumerable<T> Flatten<T>(this IEnumerable<T> input, Func<T, IEnumerable<T>> recursion)
-		{
-			Stack<IEnumerator<T>> stack = new Stack<IEnumerator<T>>();
-			try {
-				stack.Push(input.GetEnumerator());
-				while (stack.Count > 0) {
-					while (stack.Peek().MoveNext()) {
-						T element = stack.Peek().Current;
-						yield return element;
-						IEnumerable<T> children = recursion(element);
-						if (children != null) {
-							stack.Push(children.GetEnumerator());
-						}
-					}
-					stack.Pop().Dispose();
-				}
-			} finally {
-				while (stack.Count > 0) {
-					stack.Pop().Dispose();
-				}
-			}
-		}
-	}
-}