Index: Core/Components/src/Core.Components.GraphSharp.Forms/Extensions/TextBlockExtensions.cs
===================================================================
diff -u -r62923c1147ab44c7716d00174a795101affc0178 -rd09f1d9a3ec9133e8a671db7131e5f92de8f0ea4
--- Core/Components/src/Core.Components.GraphSharp.Forms/Extensions/TextBlockExtensions.cs	(.../TextBlockExtensions.cs)	(revision 62923c1147ab44c7716d00174a795101affc0178)
+++ Core/Components/src/Core.Components.GraphSharp.Forms/Extensions/TextBlockExtensions.cs	(.../TextBlockExtensions.cs)	(revision d09f1d9a3ec9133e8a671db7131e5f92de8f0ea4)
@@ -46,12 +46,17 @@
         
         private static void FormattedTextChanged(DependencyObject sender, DependencyPropertyChangedEventArgs eventArgs)
         {
-            var value = eventArgs.NewValue as string;
             var textBlock = sender as TextBlock;
+            if (textBlock == null)
+            {
+                return;
+            }
 
-            if (textBlock != null)
+            textBlock.Inlines.Clear();
+
+            var value = eventArgs.NewValue as string;
+            if (value != null)
             {
-                textBlock.Inlines.Clear();
                 textBlock.Inlines.Add(Convert(value));
             }
         }
Index: Core/Components/src/Core.Components.GraphSharp.Forms/PointedTreeGraphControl.cs
===================================================================
diff -u -r672857a9fcd0dfdcaec314524d580af98894536f -rd09f1d9a3ec9133e8a671db7131e5f92de8f0ea4
--- Core/Components/src/Core.Components.GraphSharp.Forms/PointedTreeGraphControl.cs	(.../PointedTreeGraphControl.cs)	(revision 672857a9fcd0dfdcaec314524d580af98894536f)
+++ Core/Components/src/Core.Components.GraphSharp.Forms/PointedTreeGraphControl.cs	(.../PointedTreeGraphControl.cs)	(revision d09f1d9a3ec9133e8a671db7131e5f92de8f0ea4)
@@ -42,7 +42,6 @@
     {
         private readonly List<DrawnGraphNode> drawnGraphNodeList = new List<DrawnGraphNode>();
         private ZoomControl zoomControl;
-        private PointedTreeGraphLayout graphLayout;
         private GraphNode data;
         private PointedTreeGraph graph;
 
@@ -54,7 +53,7 @@
         public PointedTreeGraphControl()
         {
             InitializeComponent();
-            InitializeGraph();
+            InitializeZoomControl();
         }
 
         public GraphNode Data
@@ -66,6 +65,7 @@
             set
             {
                 ClearData();
+                CreateNewGraph();
 
                 data = value;
 
@@ -88,7 +88,7 @@
             base.Dispose(disposing);
         }
 
-        private void InitializeGraph()
+        private void InitializeZoomControl()
         {
             zoomControl = new ZoomControl
             {
@@ -97,12 +97,6 @@
                 ZoomDeltaMultiplier = 300
             };
 
-            graphLayout = new PointedTreeGraphLayout();
-
-            graph = new PointedTreeGraph();
-            graphLayout.Graph = graph;
-
-            zoomControl.Content = graphLayout;
             zoomControl.PreviewMouseWheel += ZoomControl_MouseWheel;
 
             var myResourceDictionary = new ResourceDictionary
@@ -111,6 +105,8 @@
             };
             zoomControl.Resources.MergedDictionaries.Add(myResourceDictionary);
             wpfElementHost.Child = zoomControl;
+
+            CreateNewGraph();
         }
 
         private void ClearData()
@@ -120,10 +116,18 @@
                 drawnGraphNode.Vertex.PropertyChanged -= VertexOnPropertyChanged;
             }
 
-            graph.Clear();
             drawnGraphNodeList.Clear();
         }
 
+        private void CreateNewGraph()
+        {
+            graph = new PointedTreeGraph();
+            zoomControl.Content = new PointedTreeGraphLayout
+            {
+                Graph = graph
+            };
+        }
+
         private void DrawNode(GraphNode node, PointedTreeElementVertex parentVertex = null)
         {
             PointedTreeElementVertex vertex = GraphNodeConverter.Convert(node);
@@ -177,6 +181,22 @@
             SelectionChanged?.Invoke(this, e);
         }
 
+        /// <summary>
+        /// Lookup class for administration related to drawn vertices.
+        /// </summary>
+        private class DrawnGraphNode
+        {
+            /// <summary>
+            /// The graph node which the drawn <see cref="PointedTreeElementVertex "/> is based upon.
+            /// </summary>
+            public GraphNode GraphNode { get; set; }
+
+            /// <summary>
+            /// The drawn vertex.
+            /// </summary>
+            public PointedTreeElementVertex Vertex { get; set; }
+        }
+
         #region Zooming
 
         private void ZoomControl_MouseWheel(object sender, MouseWheelEventArgs e)
@@ -207,21 +227,5 @@
         }
 
         #endregion
-
-        /// <summary>
-        /// Lookup class for administration related to drawn vertices.
-        /// </summary>
-        private class DrawnGraphNode
-        {
-            /// <summary>
-            /// The graph node which the drawn <see cref="PointedTreeElementVertex "/> is based upon.
-            /// </summary>
-            public GraphNode GraphNode { get; set; }
-
-            /// <summary>
-            /// The drawn vertex.
-            /// </summary>
-            public PointedTreeElementVertex Vertex { get; set; }
-        }
     }
 }
\ No newline at end of file
Index: Core/Components/test/Core.Components.GraphSharp.Forms.Test/Extensions/TextBlockExtensionsTest.cs
===================================================================
diff -u -r62923c1147ab44c7716d00174a795101affc0178 -rd09f1d9a3ec9133e8a671db7131e5f92de8f0ea4
--- Core/Components/test/Core.Components.GraphSharp.Forms.Test/Extensions/TextBlockExtensionsTest.cs	(.../TextBlockExtensionsTest.cs)	(revision 62923c1147ab44c7716d00174a795101affc0178)
+++ Core/Components/test/Core.Components.GraphSharp.Forms.Test/Extensions/TextBlockExtensionsTest.cs	(.../TextBlockExtensionsTest.cs)	(revision d09f1d9a3ec9133e8a671db7131e5f92de8f0ea4)
@@ -126,6 +126,31 @@
 
         [Test]
         [Apartment(ApartmentState.STA)]
+        public void GivenTextBlockWithXml_WhenNewTextXmlNull_ThenInlinesCleared()
+        {
+            // Given
+            const string xmlToConvert = "<text>test</text>";
+            var textBlock = new TextBlock();
+
+            TextBlockExtensions.SetFormattedText(textBlock, xmlToConvert);
+
+            // Precondition
+            Assert.AreEqual(1, textBlock.Inlines.Count);
+            var span = (Span) textBlock.Inlines.First();
+
+            Assert.AreEqual(1, span.Inlines.Count);
+            var run = (Run) span.Inlines.First();
+            Assert.AreEqual("test", run.Text);
+
+            // When
+            TextBlockExtensions.SetFormattedText(textBlock, null);
+
+            // Then
+            CollectionAssert.IsEmpty(textBlock.Inlines);
+        }
+
+        [Test]
+        [Apartment(ApartmentState.STA)]
         public void GetFormattedText_DefaultValue_ReturnNull()
         {
             // Setup
@@ -136,7 +161,6 @@
 
             // Assert
             Assert.IsNull(formattedText);
-
         }
 
         [Test]
@@ -146,7 +170,7 @@
             // Setup
             const string xmlToConvert = "<text>test <bold>bold text</bold></text>";
             var textBlock = new TextBlock();
-            
+
             TextBlockExtensions.SetFormattedText(textBlock, xmlToConvert);
 
             // Call
Index: Core/Components/test/Core.Components.GraphSharp.Forms.Test/PointedTreeGraphControlTest.cs
===================================================================
diff -u -r616979c00d24e9ad678e1c945a15e3c38fa49391 -rd09f1d9a3ec9133e8a671db7131e5f92de8f0ea4
--- Core/Components/test/Core.Components.GraphSharp.Forms.Test/PointedTreeGraphControlTest.cs	(.../PointedTreeGraphControlTest.cs)	(revision 616979c00d24e9ad678e1c945a15e3c38fa49391)
+++ Core/Components/test/Core.Components.GraphSharp.Forms.Test/PointedTreeGraphControlTest.cs	(.../PointedTreeGraphControlTest.cs)	(revision d09f1d9a3ec9133e8a671db7131e5f92de8f0ea4)
@@ -86,14 +86,17 @@
                     }, false)
                 }, false);
 
+                PointedTreeGraph originalGraph = PointedTreeGraphControlHelper.GetPointedTreeGraph(graphControl);
+
                 // When
                 graphControl.Data = node;
 
                 // Then
-                PointedTreeGraph graph = PointedTreeGraphControlHelper.GetPointedTreeGraph(graphControl);
+                PointedTreeGraph newGraph = PointedTreeGraphControlHelper.GetPointedTreeGraph(graphControl);
 
-                Assert.AreEqual(5, graph.VertexCount);
-                Assert.AreEqual(4, graph.EdgeCount);
+                Assert.AreNotSame(originalGraph, newGraph);
+                Assert.AreEqual(5, newGraph.VertexCount);
+                Assert.AreEqual(4, newGraph.EdgeCount);
             }
         }
 
@@ -121,6 +124,7 @@
                 graphControl.Data = new GraphNode("<text>Double used</text>", new GraphNode[0], false);
 
                 // Then
+                graph = PointedTreeGraphControlHelper.GetPointedTreeGraph(graphControl);
                 Assert.AreEqual(1, graph.VertexCount);
                 Assert.AreEqual(0, graph.EdgeCount);
             }
@@ -150,6 +154,7 @@
                 graphControl.Data = null;
 
                 // Then
+                graph = PointedTreeGraphControlHelper.GetPointedTreeGraph(graphControl);
                 Assert.AreEqual(0, graph.VertexCount);
                 Assert.AreEqual(0, graph.EdgeCount);
             }