Stroll of the navigator...

src/Microsoft.Data.Entity/ChangeTracking/NavigationFixer.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
 using System.Linq;
 using JetBrains.Annotations;
 using Microsoft.Data.Entity.Metadata;
@@ -13,8 +12,7 @@ namespace Microsoft.Data.Entity.ChangeTracking
     public class NavigationFixer : IEntityStateListener
     {
         private readonly StateManager _stateManager;
-        private readonly ClrCollectionAccessorSource _collectionAccessorSource;
-        private readonly ClrPropertySetterSource _setterSource;
+        private readonly NavigationAccessorSource _accessorSource;
 
         /// <summary>
         ///     This constructor is intended only for use when creating test doubles that will override members
@@ -27,16 +25,13 @@ protected NavigationFixer()
 
         public NavigationFixer(
             [NotNull] StateManager stateManager,
-            [NotNull] ClrCollectionAccessorSource collectionAccessorSource,
-            [NotNull] ClrPropertySetterSource setterSource)
+            [NotNull] NavigationAccessorSource accessorSource)
         {
             Check.NotNull(stateManager, "stateManager");
-            Check.NotNull(collectionAccessorSource, "collectionAccessorSource");
-            Check.NotNull(setterSource, "setterSource");
+            Check.NotNull(accessorSource, "accessorSource");
 
             _stateManager = stateManager;
-            _collectionAccessorSource = collectionAccessorSource;
-            _setterSource = setterSource;
+            _accessorSource = accessorSource;
         }
 
         public virtual void StateChanging(StateEntry entry, EntityState newState)
@@ -81,37 +76,33 @@ private void DoFixup(IForeignKey foreignKey, StateEntry principalEntry, StateEnt
         {
             foreach (var navigation in _stateManager.Model.GetNavigations(foreignKey))
             {
+                var accessor = _accessorSource.GetAccessor(navigation);
+
                 if (navigation.PointsToPrincipal)
                 {
-                    var accessor = _setterSource.GetAccessor(navigation);
-
                     foreach (var dependent in dependentEntries)
                     {
-                        accessor.SetClrValue(dependent.Entity, principalEntry.Entity);
+                        accessor.Setter.SetClrValue(dependent.Entity, principalEntry.Entity);
                     }
                 }
                 else
                 {
-                    // TODO: Avoid doing this lookup every time--should be cached
-                    if (navigation.EntityType.Type.GetAnyProperty(navigation.Name).PropertyType.TryGetElementType(typeof(IEnumerable<>)) == null)
-                    {
-                        var accessor = _setterSource.GetAccessor(navigation);
-
-                        // TODO: Decide how to handle case where multiple values match non-collection nav prop
-                        accessor.SetClrValue(principalEntry.Entity, dependentEntries.Single().Entity);
-                    }
-                    else
+                    var collectionAccessor = accessor as CollectionNavigationAccessor;
+                    if (collectionAccessor != null)
                     {
-                        var accessor = _collectionAccessorSource.GetAccessor(navigation);
-
                         foreach (var dependent in dependentEntries)
                         {
-                            if (!accessor.Contains(principalEntry.Entity, dependent.Entity))
+                            if (!collectionAccessor.Collection.Contains(principalEntry.Entity, dependent.Entity))
                             {
-                                accessor.Add(principalEntry.Entity, dependent.Entity);
+                                collectionAccessor.Collection.Add(principalEntry.Entity, dependent.Entity);
                             }
                         }
                     }
+                    else
+                    {
+                        // TODO: Decide how to handle case where multiple values match non-collection nav prop
+                        accessor.Setter.SetClrValue(principalEntry.Entity, dependentEntries.Single().Entity);
+                    }
                 }
             }
         }

src/Microsoft.Data.Entity/Extensions/EntityServiceCollectionExtensions.cs

@@ -29,6 +29,7 @@ public static EntityServicesBuilder AddEntityFramework([NotNull] this IServiceCo
                 .AddSingleton<ClrPropertyGetterSource>()
                 .AddSingleton<ClrPropertySetterSource>()
                 .AddSingleton<ClrCollectionAccessorSource>()
+                .AddSingleton<NavigationAccessorSource>()
                 .AddSingleton<EntityMaterializerSource>()
                 .AddSingleton<CompositeEntityKeyFactory>()
                 .AddSingleton<MemberMapper>()

src/Microsoft.Data.Entity/Metadata/CollectionNavigationAccessor.cs

@@ -0,0 +1,30 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using JetBrains.Annotations;
+using Microsoft.Data.Entity.Utilities;
+
+namespace Microsoft.Data.Entity.Metadata
+{
+    public class CollectionNavigationAccessor : NavigationAccessor
+    {
+        private readonly ThreadSafeLazyRef<IClrCollectionAccessor> _collectionAccessor;
+
+        public CollectionNavigationAccessor(
+            [NotNull] Func<IClrPropertyGetter> getter,
+            [NotNull] Func<IClrPropertySetter> setter,
+            [NotNull] Func<IClrCollectionAccessor> collectionAccessor)
+            : base(getter, setter)
+        {
+            Check.NotNull(collectionAccessor, "collectionAccessor");
+
+            _collectionAccessor = new ThreadSafeLazyRef<IClrCollectionAccessor>(collectionAccessor);
+        }
+
+        public virtual IClrCollectionAccessor Collection
+        {
+            get { return _collectionAccessor.Value; }
+        }
+    }
+}

src/Microsoft.Data.Entity/Metadata/NavigationAccessor.cs

@@ -0,0 +1,36 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using JetBrains.Annotations;
+using Microsoft.Data.Entity.Utilities;
+
+namespace Microsoft.Data.Entity.Metadata
+{
+    public class NavigationAccessor
+    {
+        private readonly ThreadSafeLazyRef<IClrPropertyGetter> _getter;
+        private readonly ThreadSafeLazyRef<IClrPropertySetter> _setter;
+
+        public NavigationAccessor(
+            [NotNull] Func<IClrPropertyGetter> getter,
+            [NotNull] Func<IClrPropertySetter> setter)
+        {
+            Check.NotNull(getter, "getter");
+            Check.NotNull(setter, "setter");
+
+            _getter = new ThreadSafeLazyRef<IClrPropertyGetter>(getter);
+            _setter = new ThreadSafeLazyRef<IClrPropertySetter>(setter);
+        }
+
+        public virtual IClrPropertyGetter Getter
+        {
+            get { return _getter.Value; }
+        }
+
+        public virtual IClrPropertySetter Setter
+        {
+            get { return _setter.Value; }
+        }
+    }
+}

src/Microsoft.Data.Entity/Metadata/NavigationAccessorSource.cs

@@ -0,0 +1,64 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using JetBrains.Annotations;
+using Microsoft.Data.Entity.Utilities;
+
+namespace Microsoft.Data.Entity.Metadata
+{
+    public class NavigationAccessorSource
+    {
+        private readonly ThreadSafeDictionaryCache<Tuple<Type, string>, NavigationAccessor> _cache
+            = new ThreadSafeDictionaryCache<Tuple<Type, string>, NavigationAccessor>();
+
+        private readonly ClrCollectionAccessorSource _collectionAccessorSource;
+        private readonly ClrPropertySetterSource _setterSource;
+        private readonly ClrPropertyGetterSource _getterSource;
+
+        public NavigationAccessorSource(
+            [NotNull] ClrPropertyGetterSource getterSource,
+            [NotNull] ClrPropertySetterSource setterSource,
+            [NotNull] ClrCollectionAccessorSource collectionAccessorSource)
+        {
+            Check.NotNull(getterSource, "getterSource");
+            Check.NotNull(setterSource, "setterSource");
+            Check.NotNull(collectionAccessorSource, "collectionAccessorSource");
+
+            _getterSource = getterSource;
+            _setterSource = setterSource;
+            _collectionAccessorSource = collectionAccessorSource;
+        }
+
+        public virtual NavigationAccessor GetAccessor([NotNull] INavigation navigation)
+        {
+            Check.NotNull(navigation, "navigation");
+
+            return _cache.GetOrAdd(
+                Tuple.Create(navigation.EntityType.Type, navigation.Name),
+                k => Create(navigation));
+        }
+
+        private NavigationAccessor Create(INavigation navigation)
+        {
+            var elementType = navigation.EntityType.Type.GetAnyProperty(navigation.Name).PropertyType.TryGetElementType(typeof(IEnumerable<>));
+
+            var targetType = navigation.PointsToPrincipal
+                ? navigation.ForeignKey.ReferencedEntityType
+                : navigation.ForeignKey.EntityType;
+
+            // TODO: Consider allowing an annotation to force treating a reference to an Entity which is an IEnumerable of
+            // itself as a reference instead of a collection. Currently it will be considered a collection nav prop, which it isn't.
+
+            return elementType != null && elementType == targetType.Type
+                ? new CollectionNavigationAccessor(
+                    () => _getterSource.GetAccessor(navigation),
+                    () => _setterSource.GetAccessor(navigation),
+                    () => _collectionAccessorSource.GetAccessor(navigation))
+                : new NavigationAccessor(
+                    () => _getterSource.GetAccessor(navigation),
+                    () => _setterSource.GetAccessor(navigation));
+        }
+    }
+}

src/Microsoft.Data.Entity/Microsoft.Data.Entity.csproj

@@ -75,6 +75,9 @@
     <Compile Include="Identity\ValueGeneratorSelector.cs" />
     <Compile Include="Infrastructure\IDbContextOptionsExtensions.cs" />
     <Compile Include="INotifyPropertyChanging.cs" />
+    <Compile Include="Metadata\CollectionNavigationAccessor.cs" />
+    <Compile Include="Metadata\NavigationAccessor.cs" />
+    <Compile Include="Metadata\NavigationAccessorSource.cs" />
     <Compile Include="Query\AsyncQueryCompilationContext.cs" />
     <Compile Include="Query\AsyncResultOperatorHandler.cs" />
     <Compile Include="Query\IResultOperatorHandler.cs" />