diff --git a/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/Layout/GraphMatcher.cs b/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/Layout/GraphMatcher.cs
index e8a583c588..3dc739887c 100644
--- a/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/Layout/GraphMatcher.cs
+++ b/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/Layout/GraphMatcher.cs
@@ -94,7 +94,7 @@ namespace Debugger.AddIn.Visualizers.Graph.Layout
 		
 		private bool isSameAddress(PositionedNode node1, PositionedNode node2)
 		{
-			return node1.ObjectNode.PermanentReference.GetObjectAddress() == node2.ObjectNode.PermanentReference.GetObjectAddress();
+			return node1.ObjectNode.DebuggerValue.GetObjectAddress() == node2.ObjectNode.DebuggerValue.GetObjectAddress();
 		}
 	}
 }
diff --git a/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/ObjectGraph/ObjectGraphBuilder.cs b/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/ObjectGraph/ObjectGraphBuilder.cs
index 5daaabf17d..87ca058879 100644
--- a/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/ObjectGraph/ObjectGraphBuilder.cs
+++ b/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/ObjectGraph/ObjectGraphBuilder.cs
@@ -43,10 +43,13 @@ namespace Debugger.AddIn.Visualizers.Graph
 		/// The underlying debugger service used for getting expression values.
 		/// </summary>
 		private WindowsDebugger debuggerService;
+
+		private ObjectGraph resultGraph;
 		/// <summary>
-		/// The resulting object graph.
+		/// Underlying object graph data struture.
 		/// </summary>
-		private ObjectGraph resultGraph;
+		public ObjectGraph ResultGraph { get { return this.resultGraph; } }
+		
 		/// <summary>
 		/// System.Runtime.CompilerServices.GetHashCode method, for obtaining non-overriden hash codes from debuggee.
 		/// </summary>
@@ -60,7 +63,7 @@ namespace Debugger.AddIn.Visualizers.Graph
 		/// <summary>
 		/// Binding flags for getting member expressions.
 		/// </summary>
-		private readonly Debugger.MetaData.BindingFlags _bindingFlags = 
+		private readonly Debugger.MetaData.BindingFlags _bindingFlags =
 			BindingFlags.Public | BindingFlags.Instance | BindingFlags.Field | BindingFlags.GetProperty;
 		
 		/// <summary>
@@ -92,37 +95,52 @@ namespace Debugger.AddIn.Visualizers.Graph
 			// empty graph for null expression
 			if (!debuggerService.GetValueFromName(expression).IsNull)
 			{
-				resultGraph.Root = buildGraphRecursive(debuggerService.GetValueFromName(expression).GetPermanentReference(), expandedNodes);
+				//resultGraph.Root = buildGraphRecursive(debuggerService.GetValueFromName(expression).GetPermanentReference(), expandedNodes);
+				resultGraph.Root = createNewNode(debuggerService.GetValueFromName(expression).GetPermanentReference());
+				loadNodeProperties(resultGraph.Root);
+				loadChildrenRecursive(resultGraph.Root, expandedNodes);
 			}
 			
 			return resultGraph;
 		}
 		
+		public ObjectNode ObtainNodeForExpression(Expression expr, out bool createdNewNode)
+		{
+			return ObtainNodeForValue(getPermanentReference(expr), out createdNewNode);
+		}
+		
+		public ObjectNode ObtainNodeForExpression(Expression expr)
+		{
+			bool createdNewNode; // ignore (caller is not interested, otherwise he would use the other overload)
+			return ObtainNodeForExpression(expr, out createdNewNode);
+		}
+		
 		/// <summary>
-		/// Builds the subgraph representing given value.
+		/// Returns node in the graph that represents given value, or returns new node if no node found.
 		/// </summary>
-		/// <param name="rootValue">The Value for which the subgraph will be built.</param>
-		/// <returns>ObjectNode representing the value + all recursive members.</returns>
-		private ObjectNode buildGraphRecursive(Value rootValue, ExpandedNodes expandedNodes)
+		/// <param name="value">Value for which to obtain the node/</param>
+		/// <param name="createdNew">True if new node was created, false if existing node was returned.</param>
+		public ObjectNode ObtainNodeForValue(Value value, out bool createdNew)
 		{
-			ObjectNode thisNode = createNewNode(rootValue); 
-			
-			// David: by calling this, we get an array of values, most of them probably invalid,
-			// it would be nice to be able to get a collection of 'values' 
-			// that are valid (basically a snapshot of object's state)
-			// - a collection of custom objects, 
-			// that contain the string value and DebugType,
-			// and can enumerate child values.
-			// It would be also nice to return IEnumerable or ReadonlyCollection
-			// http://blogs.msdn.com/ericlippert/archive/2008/09/22/arrays-considered-somewhat-harmful.aspx
-			/*string[] memberValues = rootValue.GetMemberValuesAsString(_bindingFlags);
-			foreach	(string memberValue in memberValues)
+			createdNew = false;
+			ObjectNode nodeForValue = getExistingNodeForValue(value);
+			if (nodeForValue == null)
 			{
-				//Value memberValuePerm = memberValue.GetPermanentReference();
-				
-			}*/
-			
-			foreach(Expression memberExpr in rootValue.Expression.AppendObjectMembers(rootValue.Type, _bindingFlags))
+				// if no node for memberValue exists, create it
+				nodeForValue = createNewNode(value);
+				loadNodeProperties(nodeForValue);
+				createdNew = true;
+			}
+			return nodeForValue;
+		}
+		
+		/// <summary>
+		/// Fills node contents by adding properties.
+		/// </summary>
+		/// <param name="thisNode"></param>
+		private void loadNodeProperties(ObjectNode thisNode)
+		{
+			foreach(Expression memberExpr in thisNode.DebuggerValue.Expression.AppendObjectMembers(thisNode.DebuggerValue.Type, _bindingFlags))
 			{
 				checkIsOfSupportedType(memberExpr);
 				
@@ -131,34 +149,48 @@ namespace Debugger.AddIn.Visualizers.Graph
 				{
 					// atomic members are added to the list of node's "properties"
 					string memberValueAsString = memberExpr.Evaluate(debuggerService.DebuggedProcess).AsString;
-				    thisNode.AddAtomicProperty(memberName, memberValueAsString, memberExpr);
+					thisNode.AddAtomicProperty(memberName, memberValueAsString, memberExpr);
 				}
 				else
 				{
+					// for object members, complex properties are added
 					ObjectNode targetNode = null;
 					bool memberIsNull = isNull(memberExpr);
-					if (!memberIsNull && expandedNodes.IsExpanded(memberExpr.Code))
-					{
-						// for object members, edges are added
-						Value memberValue = getPermanentReference(memberExpr);
-						
-						// if node for memberValue already exists, only add edge to it (so loops etc. are solved correctly)
-						targetNode = getNodeForValue(memberValue);
-						if (targetNode == null)
-						{
-							// if no node for memberValue exists, build the subgraph for the value
-							targetNode = buildGraphRecursive(memberValue, expandedNodes);
-						}
-					}
-					else 
+					thisNode.AddComplexProperty(memberName, "", memberExpr, targetNode, memberIsNull);
+				}
+			}
+		}
+		
+		/// <summary>
+		/// Creates child nodes of this node for each complex property and connects them to property.TargetNode.
+		/// </summary>
+		/// <param name="thisNode"></param>
+		/// <param name="expandedNodes"></param>
+		private void loadChildrenRecursive(ObjectNode thisNode, ExpandedNodes expandedNodes)
+		{
+			foreach(ObjectProperty complexProperty in thisNode.ComplexProperties)
+			{
+				Expression memberExpr = complexProperty.Expression;
+				ObjectNode targetNode = null;
+				if (!complexProperty.IsNull && expandedNodes.IsExpanded(memberExpr.Code))
+				{
+					Value memberValue = getPermanentReference(memberExpr);
+					
+					bool createdNew;
+					// get existing node (loop) or create new
+					targetNode = ObtainNodeForValue(memberValue, out createdNew);
+					if (createdNew)
 					{
-						targetNode = null;
+						// if member node is new, recursively build its subtree
+						loadChildrenRecursive(targetNode, expandedNodes);
 					}
-					thisNode.AddComplexProperty(memberName, "", memberExpr, targetNode, memberIsNull);
 				}
+				else
+				{
+					targetNode = null;
+				}
+				complexProperty.TargetNode = targetNode;
 			}
-			
-			return thisNode;
 		}
 		
 		/// <summary>
@@ -175,9 +207,9 @@ namespace Debugger.AddIn.Visualizers.Graph
 			// remember this node's hashcode for quick lookup
 			objectNodesForHashCode.Add(newNode.HashCode, newNode);
 			
-			// permanent reference to the object this node represents is useful for graph building, 
+			// permanent reference to the object this node represents is useful for graph building,
 			// and matching nodes in animations
-			newNode.PermanentReference = permanentReference;
+			newNode.DebuggerValue = permanentReference;
 			
 			return newNode;
 		}
@@ -187,7 +219,7 @@ namespace Debugger.AddIn.Visualizers.Graph
 		/// </summary>
 		/// <param name="value">Valid value representing an instance.</param>
 		/// <returns></returns>
-		private ObjectNode getNodeForValue(Value value)
+		private ObjectNode getExistingNodeForValue(Value value)
 		{
 			int objectHashCode = invokeGetHashCode(value);
 			// are there any nodes with the same hash code?
@@ -202,7 +234,7 @@ namespace Debugger.AddIn.Visualizers.Graph
 				// (hash codes are not uniqe - http://stackoverflow.com/questions/750947/-net-unique-object-identifier)
 				ulong objectAddress = value.GetObjectAddress();
 				ObjectNode nodeWithSameAddress = nodesWithSameHashCode.Find(
-					node => { return objectAddress == node.PermanentReference.GetObjectAddress(); } );
+					node => { return node.DebuggerValue.GetObjectAddress() == objectAddress; } );
 				return nodeWithSameAddress;
 			}
 		}
@@ -251,7 +283,7 @@ namespace Debugger.AddIn.Visualizers.Graph
 		}
 		
 		#region Expression helpers
-			
+		
 		private Value getPermanentReference(Expression expr)
 		{
 			return expr.Evaluate(debuggerService.DebuggedProcess).GetPermanentReference();
diff --git a/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/ObjectGraph/ObjectNode.cs b/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/ObjectGraph/ObjectNode.cs
index 61ecc65193..562fad418c 100644
--- a/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/ObjectGraph/ObjectNode.cs
+++ b/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/ObjectGraph/ObjectNode.cs
@@ -17,10 +17,17 @@ namespace Debugger.AddIn.Visualizers.Graph
 	public class ObjectNode
 	{
 		/// <summary>
-		/// Additional info useful for internal algorithms, not to be visible to the user.
+		/// Permanent reference to the value in the the debugee this node represents.
+		/// </summary>
+		internal Debugger.Value DebuggerValue { get; set; }
+		/// <summary>
+		/// Hash code in the debuggee of the DebuggerValue this node represents.
 		/// </summary>
-		internal Debugger.Value PermanentReference { get; set; }
 		internal int HashCode { get; set; }
+		/// <summary>
+		/// Expression used to obtain this node.
+		/// </summary>
+		public Expressions.Expression Expression { get { return this.DebuggerValue.Expression; } }
 		
 		/*private List<ObjectEdge> _edges = new List<ObjectEdge>();
         /// <summary>
diff --git a/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/VisualizerWPFWindow.xaml.cs b/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/VisualizerWPFWindow.xaml.cs
index 08457c8a09..05efc25f66 100644
--- a/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/VisualizerWPFWindow.xaml.cs
+++ b/src/AddIns/Misc/Debugger/Debugger.AddIn/Project/Src/Visualizers/Graph/VisualizerWPFWindow.xaml.cs
@@ -31,9 +31,10 @@ namespace Debugger.AddIn.Visualizers.Graph
     	private WindowsDebugger debuggerService;
     	private EnumViewModel<LayoutDirection> layoutViewModel;
     	private ObjectGraph objectGraph;
+    	private ObjectGraphBuilder objectGraphBuilder;
     	
-    	private PositionedGraph oldGraph;
-    	private PositionedGraph currentGraph;
+    	private PositionedGraph oldPosGraph;
+    	private PositionedGraph currentPosGraph;
     	private GraphDrawer graphDrawer;
     	
     	/// <summary>
@@ -91,42 +92,43 @@ namespace Debugger.AddIn.Visualizers.Graph
         
         void refreshGraph()
 		{
-			ObjectGraphBuilder graphBuilder = new ObjectGraphBuilder(debuggerService);
-			this.objectGraph = null;
-			
+        	this.objectGraph = rebuildGraph();
+			layoutGraph(this.objectGraph);	
+			//GraphDrawer drawer = new GraphDrawer(graph);
+			//drawer.Draw(canvas);
+		}
+        
+        ObjectGraph rebuildGraph()
+        {
+        	this.objectGraphBuilder = new ObjectGraphBuilder(debuggerService);
 			try
 			{	
 				ICSharpCode.Core.LoggingService.Debug("Debugger visualizer: Building graph for expression: " + txtExpression.Text);
-				this.objectGraph = graphBuilder.BuildGraphForExpression(txtExpression.Text, expandedNodes);
+				return this.objectGraphBuilder.BuildGraphForExpression(txtExpression.Text, this.expandedNodes);
 			}
 			catch(DebuggerVisualizerException ex)
 			{
 				guiHandleException(ex);
-				return;
+				return null;
 			}
 			catch(Debugger.GetValueException ex)
 			{
 				guiHandleException(ex);
-				return;
+				return null;
 			}
-			
-			layoutGraph(this.objectGraph);
-				
-			//GraphDrawer drawer = new GraphDrawer(graph);
-			//drawer.Draw(canvas);
-		}
+        }
         
         void layoutGraph(ObjectGraph graph)
         {
         	ICSharpCode.Core.LoggingService.Debug("Debugger visualizer: Calculating graph layout");
         	Layout.TreeLayouter layouter = new Layout.TreeLayouter();
         	
-            this.oldGraph = this.currentGraph;
-			this.currentGraph = layouter.CalculateLayout(graph, layoutViewModel.SelectedEnumValue, this.expandedNodes);
-			registerExpandCollapseEvents(this.currentGraph);
+            this.oldPosGraph = this.currentPosGraph;
+			this.currentPosGraph = layouter.CalculateLayout(graph, layoutViewModel.SelectedEnumValue, this.expandedNodes);
+			registerExpandCollapseEvents(this.currentPosGraph);
 			
-			var graphDiff = new GraphMatcher().MatchGraphs(oldGraph, currentGraph);
-			this.graphDrawer.StartAnimation(oldGraph, currentGraph, graphDiff);
+			var graphDiff = new GraphMatcher().MatchGraphs(oldPosGraph, currentPosGraph);
+			this.graphDrawer.StartAnimation(oldPosGraph, currentPosGraph, graphDiff);
 			//this.graphDrawer.Draw(currentGraph);
         }
 		
@@ -146,14 +148,22 @@ namespace Debugger.AddIn.Visualizers.Graph
 
 		void node_Expanded(object sender, PositionedPropertyEventArgs e)
 		{
+			// remember this property is expanded (for later graph rebuilds)
 			expandedNodes.SetExpanded(e.Property.Expression.Code);
-			refreshGraph();
+			
+			// add edge (+ possibly node) to underlying object graph (no need to rebuild)
+			e.Property.ObjectProperty.TargetNode = this.objectGraphBuilder.ObtainNodeForExpression(e.Property.Expression);
+			layoutGraph(this.objectGraph);
 		}
 		
 		void node_Collapsed(object sender, PositionedPropertyEventArgs e)
 		{
+			// remember this property is collapsed (for later graph rebuilds)
 			expandedNodes.SetCollapsed(e.Property.Expression.Code);
-			refreshGraph();
+			
+			// just remove edge from underlying object graph (no need to rebuild)
+			e.Property.ObjectProperty.TargetNode = null;
+			layoutGraph(this.objectGraph);
 		}
     }
 }
\ No newline at end of file