adding a few tests for areas

src/Microsoft.AspNet.Mvc.Core/ReflectedActionDescriptorProvider.cs

@@ -272,6 +272,18 @@ namespace Microsoft.AspNet.Mvc
                                 RouteKeyHandling.DenyKey));
                         }
                     }
+                    else
+                    {
+                        // We still want to add a 'null' for any constraint with DenyKey so that link generation
+                        // works properly.
+                        //
+                        // Consider an action like { area = "", controller = "Home", action = "Index" }. Even if
+                        // it's attribute routed, it needs to know that area must be null to generate a link.
+                        if (!actionDescriptor.RouteValueDefaults.ContainsKey(key))
+                        {
+                            actionDescriptor.RouteValueDefaults.Add(key, null);
+                        }
+                    }
                 }
             }
 

src/Microsoft.AspNet.Mvc.Core/Routing/AttributeRoute.cs

@@ -171,7 +171,15 @@ namespace Microsoft.AspNet.Mvc.Routing
             object providedValue;
             if (!context.Values.TryGetValue(key, out providedValue))
             {
-                context.AmbientValues.TryGetValue(key, out providedValue);
+                // If the required value is an 'empty' route value, then ignore ambient values.
+                // This handles a case where we're generating a link to an action like:
+                // { area = "", controller = "Home", action = "Index" } 
+                //
+                // and the ambient values has a value for area.
+                if (value != null)
+                {
+                    context.AmbientValues.TryGetValue(key, out providedValue);
+                }
             }
 
             return TemplateBinder.RoutePartsEqual(providedValue, value);

test/Microsoft.AspNet.Mvc.Core.Test/Routing/AttributeRouteTests.cs

@@ -296,6 +296,102 @@ namespace Microsoft.AspNet.Mvc.Routing
             Assert.Equal(2, callCount);
         }
 
+        [Fact]
+        public void AttributeRoute_GenerateLink_ToArea()
+        {
+            // Arrange
+            var entry1 = CreateGenerationEntry("Help/Store", new { area = "Help", action = "Edit", controller = "Store" });
+            entry1.Precedence = 1;
+
+            var entry2 = CreateGenerationEntry("Store", new { area = (string)null, action = "Edit", controller = "Store" });
+            entry2.Precedence = 2;
+
+            var next = new StubRouter();
+
+            var route = CreateAttributeRoute(next, entry1, entry2);
+
+            var context = CreateVirtualPathContext(new { area = "Help", action = "Edit", controller = "Store" });
+
+            // Act
+            var path = route.GetVirtualPath(context);
+
+            // Assert
+            Assert.Equal("Help/Store", path);
+        }
+
+        [Fact]
+        public void AttributeRoute_GenerateLink_ToArea_PredecedenceReversed()
+        {
+            // Arrange
+            var entry1 = CreateGenerationEntry("Help/Store", new { area = "Help", action = "Edit", controller = "Store" });
+            entry1.Precedence = 2;
+
+            var entry2 = CreateGenerationEntry("Store", new { area = (string)null, action = "Edit", controller = "Store" });
+            entry2.Precedence = 1;
+
+            var next = new StubRouter();
+
+            var route = CreateAttributeRoute(next, entry1, entry2);
+
+            var context = CreateVirtualPathContext(new { area = "Help", action = "Edit", controller = "Store" });
+
+            // Act
+            var path = route.GetVirtualPath(context);
+
+            // Assert
+            Assert.Equal("Help/Store", path);
+        }
+
+        [Fact]
+        public void AttributeRoute_GenerateLink_ToArea_WithAmbientValues()
+        {
+            // Arrange
+            var entry1 = CreateGenerationEntry("Help/Store", new { area = "Help", action = "Edit", controller = "Store" });
+            entry1.Precedence = 1;
+
+            var entry2 = CreateGenerationEntry("Store", new { area = (string)null, action = "Edit", controller = "Store" });
+            entry2.Precedence = 2;
+
+            var next = new StubRouter();
+
+            var route = CreateAttributeRoute(next, entry1, entry2);
+
+            var context = CreateVirtualPathContext(
+                values: new { action = "Edit", controller = "Store" },
+                ambientValues: new { area = "Help" });
+
+            // Act
+            var path = route.GetVirtualPath(context);
+
+            // Assert
+            Assert.Equal("Help/Store", path);
+        }
+
+        [Fact]
+        public void AttributeRoute_GenerateLink_OutOfArea_IgnoresAmbientValue()
+        {
+            // Arrange
+            var entry1 = CreateGenerationEntry("Help/Store", new { area = "Help", action = "Edit", controller = "Store" });
+            entry1.Precedence = 1;
+
+            var entry2 = CreateGenerationEntry("Store", new { area = (string)null, action = "Edit", controller = "Store" });
+            entry2.Precedence = 2;
+
+            var next = new StubRouter();
+
+            var route = CreateAttributeRoute(next, entry1, entry2);
+
+            var context = CreateVirtualPathContext(
+                values: new { action = "Edit", controller = "Store" },
+                ambientValues: new { area = "Blog" });
+
+            // Act
+            var path = route.GetVirtualPath(context);
+
+            // Assert
+            Assert.Equal("Store", path);
+        }
+
         private static VirtualPathContext CreateVirtualPathContext(object values, object ambientValues = null)
         {
             var httpContext = Mock.Of<HttpContext>();