Fix FxCop warnings under Release

Author: lewischeng-ms

src/Microsoft.Restier.EntityFramework/Model/ModelProducer.cs

@@ -71,10 +71,7 @@ private static IDictionary<PrimitiveTypeKind, EdmPrimitiveTypeKind>
             { PrimitiveTypeKind.Time, EdmPrimitiveTypeKind.Duration }
         };
 
-        static ModelProducer()
-        {
-            Instance = new ModelProducer();
-        }
+        private static IModelBuilder instance;
 
         private ModelProducer()
         {
@@ -83,7 +80,18 @@ private ModelProducer()
         /// <summary>
         /// Gets the single instance of this model producer.
         /// </summary>
-        public static ModelProducer Instance { get; private set; }
+        public static IModelBuilder Instance
+        {
+            get
+            {
+                if (instance == null)
+                {
+                    instance = new ModelProducer();
+                }
+
+                return instance;
+            }
+        }
 
         /// <inheritdoc/>
         public Task<IEdmModel> GetModelAsync(InvocationContext context, CancellationToken cancellationToken)

src/Microsoft.Restier.WebApi/Routing/RestierRoutingConvention.cs

@@ -115,13 +115,18 @@ private static bool HasControllerForEntitySetOrSingleton(
             ODataPathSegment firstSegment = odataPath.Segments.FirstOrDefault();
             if (firstSegment != null)
             {
-                if (firstSegment is EntitySetPathSegment)
+                var entitySetSegment = firstSegment as EntitySetPathSegment;
+                if (entitySetSegment != null)
                 {
-                    controllerName = (firstSegment as EntitySetPathSegment).EntitySetName;
+                    controllerName = entitySetSegment.EntitySetName;
                 }
-                else if (firstSegment is SingletonPathSegment)
+                else
                 {
-                    controllerName = (firstSegment as SingletonPathSegment).SingletonName;
+                    var singletonSegment = firstSegment as SingletonPathSegment;
+                    if (singletonSegment != null)
+                    {
+                        controllerName = singletonSegment.SingletonName;
+                    }
                 }
             }