diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/XmlParser/RawObjects.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/XmlParser/RawObjects.cs
index ee250fefce..5766197e6f 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/XmlParser/RawObjects.cs
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/XmlParser/RawObjects.cs
@@ -287,10 +287,7 @@ namespace ICSharpCode.AvalonEdit.XmlParser
 		/// <inheritdoc/>
 		public override IEnumerable<RawObject> GetSelfAndAllChildren()
 		{
-			return Enumerable.Union(
-				new RawContainer[] { this },
-				this.Children.SelectMany(x => x.GetSelfAndAllChildren())
-			);
+			return new RawObject[] { this }.Flatten(i => i is RawContainer ? ((RawContainer)i).Children : null);
 		}
 		
 		/// <summary>
@@ -979,4 +976,37 @@ namespace ICSharpCode.AvalonEdit.XmlParser
 			return string.Format("[{0} Text.Length={1}]", base.ToString(), this.EscapedValue.Length);
 		}
 	}
+	
+	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();
+				}
+			}
+		}
+	}
 }