Use Dictionary.TryAdd for minor perf improvements in entityset add

src/OpenRiaServices.Client/Framework/EntitySet.cs

@@ -1,14 +1,12 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.ComponentModel.DataAnnotations;
 using System.Diagnostics;
 using System.Globalization;
 using System.Linq;
-using System.Reflection;
 using OpenRiaServices.Client.Internal;
 
 #if HAS_COLLECTIONVIEW
@@ -30,7 +28,7 @@ public abstract class EntitySet : IEnumerable, ICollection, INotifyCollectionCha
         private IList _list;
         // set of entities, for fast lookup
         private HashSet<Entity> _set;
-        private IDictionary<object, Entity> _identityCache;
+        private Dictionary<object, Entity> _identityCache;
         private readonly HashSet<Entity> _interestingEntities;
         private NotifyCollectionChangedEventHandler _collectionChangedEventHandler;
 
@@ -738,7 +736,7 @@ internal Entity LoadEntity(Entity entity, LoadBehavior loadBehavior)
                 throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, Resource.EntityKey_NullIdentity, entity));
             }
 
-            Entity cachedEntity = null;
+            Entity cachedEntity;
             this._identityCache.TryGetValue(identity, out cachedEntity);
             if (cachedEntity == null)
             {
@@ -813,13 +811,11 @@ internal void AddToCache(Entity entity)
                 throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, Resource.EntityKey_NullIdentity, entity));
             }
 
-            // Throw if we already have an entity cached with the same identity
-            if (this._identityCache.ContainsKey(identity))
+            if (!this._identityCache.TryAdd(identity, entity))
             {
+                // Throw if we already have an entity cached with the same identity
                 throw new InvalidOperationException(Resource.EntitySet_DuplicateIdentity);
             }
-
-            this._identityCache[identity] = entity;
         }
 
         /// <summary>

src/OpenRiaServices.Client/Framework/Polyfills.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Collections.Generic;
+
+namespace OpenRiaServices.Client
+{
+#if !NET
+    /// <summary>
+    /// Helper methods to allow "newer" 
+    /// </summary>
+    static class Polyfills
+    {
+        public static bool TryAdd<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TValue value)
+        {
+            // This is expected to be used in scenarios where the add vill almost always succeed, so we pay the cost of an exception
+            // on duplicates instead of checking if the Key exists first
+            try
+            {
+                dictionary.Add(key, value);
+                return true;
+            }
+            // Duplicate key
+            catch (ArgumentException)
+            {
+                return false;
+            }
+        }
+    }
+#endif
+}