Created IEnumerable extension for zipping together enumerables

(so that we can easily iterate over 2 collections using their
IEnumerable interface, rather than having to index into one of them)

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Drawing/Drawer/TitleBarDrawer.cs

 using RMGUI.GraphView;
 using UnityEngine.RMGUI;
 using UnityEngine.RMGUI.StyleSheets;
+using System.Linq;
+using UnityEditor.Graphing.Util;
+using System;
 
 namespace UnityEditor.Graphing.Drawing
 {
         void UpdateContainer(VisualContainer container, IEnumerable<TitleBarButtonDrawData> itemDatas)
         {
             // The number of items can't change for now.
-            int i = 0;
-            foreach (var itemData in itemDatas)
+            foreach (var pair in itemDatas.Zip(container.children.OfType<TitleBarButtonDrawer>()))
-                var item = container.GetChildAtIndex(i) as TitleBarButtonDrawer;
-                if (item != null)
-                    item.dataProvider = itemData;
-                i++;
+                var itemData = pair.Item1;
+                var item = pair.Item2;
+                item.dataProvider = itemData;
             }
         }
 

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Util/EnumerableExtensions.cs

+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace UnityEditor.Graphing.Util
+{
+    public static class EnumerableExtensions
+    {
+        public static IEnumerable<TResult> Zip<TFirst, TSecond, TResult>(this IEnumerable<TFirst> first, IEnumerable<TSecond> second, Func<TFirst, TSecond, TResult> resultSelector)
+        {
+            var e1 = first.GetEnumerator();
+            var e2 = second.GetEnumerator();
+
+            while (e1.MoveNext() && e2.MoveNext())
+            {
+                yield return resultSelector(e1.Current, e2.Current);
+            }
+        }
+
+        public static IEnumerable<ValueTuple<TFirst, TSecond>> Zip<TFirst, TSecond>(this IEnumerable<TFirst> first, IEnumerable<TSecond> second)
+        {
+            return first.Zip(second, ValueTuple.Create);
+        }
+    }
+}

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Util/EnumerableExtensions.cs.meta

+fileFormatVersion: 2
+guid: 3042c033e57ba45458680f0259feca30
+timeCreated: 1481279276
+licenseType: Pro
+MonoImporter:
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Util/ValueTuple.cs

+using System;
+namespace UnityEditor.Graphing.Util
+{
+    public struct ValueTuple<T1, T2>
+    {
+        public T1 Item1 { get; set; }
+        public T2 Item2 { get; set; }
+
+        public ValueTuple(T1 item1, T2 item2)
+        {
+            Item1 = item1;
+            Item2 = item2;
+        }
+
+        public static ValueTuple<T1, T2> Create(T1 item1, T2 item2)
+        {
+            return new ValueTuple<T1, T2>(item1, item2);
+        }
+    }
+
+    public static class ValueTuple
+    {
+        public static ValueTuple<T1, T2> Create<T1, T2>(T1 item1, T2 item2)
+        {
+            return new ValueTuple<T1, T2>(item1, item2);
+        }
+    }
+}

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Util/ValueTuple.cs.meta

+fileFormatVersion: 2
+guid: 7fdb7b91a165649ba9e20ceaea67a970
+timeCreated: 1481279988
+licenseType: Pro
+MonoImporter:
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: