[mat graph]Readd the delete operator.

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Drawing/MaterialGraphDataSource.cs

             UpdateData();
         }
 
+        public void RemoveNodes(IEnumerable<MaterialNodeData> nodes) 
+        {
+            var toDelete = nodes.Select(x => x.node).ToList();
+            graphAsset.graph.RemoveElements(toDelete, new List<IEdge> (){});
+			graphAsset.graph.ValidateGraph();
+			UpdateData ();
+        }
+
         public IEnumerable<GraphElementData> elements
         {
             get { return m_Elements; }

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Drawing/MaterialGraphView.cs

 using System;
+using System.Linq;
 using System.Reflection;
 using RMGUI.GraphView;
 using RMGUI.GraphView.Demo;
 using UnityEngine.RMGUI;
+using System.Collections.Generic;
 using Object = UnityEngine.Object;
 
 namespace UnityEditor.Graphing.Drawing
     {
         public MaterialGraphView()
         {
+            // Shortcut handler to delete elements
+            var dictionary = new Dictionary<Event, ShortcutDelegate>();
+            dictionary[Event.KeyboardEvent("delete")] = DeleteSelection;
+            contentViewContainer.AddManipulator(new ShortcutHandler(dictionary));
+
+
             AddManipulator(new ContentZoomer());
             AddManipulator(new ContentDragger());
             AddManipulator(new RectangleSelector());
 
             dataMapper[typeof(MaterialNodeData)] = typeof(MaterialGraphNode);
             dataMapper[typeof(NodeAnchorData)] = typeof(NodeAnchor);
+        }
+
+        private EventPropagation DeleteSelection()
+        {
+            var nodalViewData = dataSource as MaterialGraphDataSource;
+            if (nodalViewData == null)
+                return EventPropagation.Stop;
+
+            // TODO We will want to move this up to GraphView
+            var elementsToRemove = new List<MaterialNodeData>();
+            foreach (var selectedElement in selection.OfType<MaterialGraphNode>())
+            {
+                var nodeData = selectedElement.dataProvider as MaterialNodeData;
+                if (nodeData != null)
+                    elementsToRemove.Add(nodeData);
+            }
+
+            nodalViewData.RemoveNodes(elementsToRemove);
+
+			return EventPropagation.Stop;
         }
 
         public virtual bool CanAddToNodeMenu(Type type)