Bug #1354 - ViewComponent View() fails on CoreCLR with IEnumerable<> …

…passed in.

Fix - When the model is passed in to a View, ViewDataDictionary sets it. During this process, we recurse through all the properties and create FastPropertyGetters for each of them. In this case, since it is an enumerable, the properties which we recurse through are not the elements of the collection but the properties of the Enumerable instead. i.e - Enumerable.Current. Creating getters for these properties are not necessary. The fix moves the property iteration step to a place where the properties are actually requested.

src/Microsoft.AspNet.Mvc.ModelBinding/Metadata/AssociatedMetadataProvider.cs

@@ -29,7 +29,8 @@ public IEnumerable<ModelMetadata> GetMetadataForProperties(object container, [No
                 throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, "propertyName");
             }
 
-            var typeInfo = GetTypeInformation(containerType);
+            var typeInfo = GetTypeInformation(containerType, getPropertyInfo: true);
+
             PropertyInformation propertyInfo;
             if (!typeInfo.Properties.TryGetValue(propertyName, out propertyInfo))
             {
@@ -92,7 +93,8 @@ public ModelMetadata GetMetadataForType(Func<object> modelAccessor, [NotNull] Ty
 
         private IEnumerable<ModelMetadata> GetMetadataForPropertiesCore(object container, Type containerType)
         {
-            var typeInfo = GetTypeInformation(containerType);
+            var typeInfo = GetTypeInformation(containerType, getPropertyInfo: true);
+
             foreach (var kvp in typeInfo.Properties)
             {
                 var propertyInfo = kvp.Value;
@@ -122,7 +124,10 @@ private TModelMetadata CreatePropertyMetadata(Func<object> modelAccessor, Proper
             return metadata;
         }
 
-        private TypeInformation GetTypeInformation(Type type, IEnumerable<Attribute> associatedAttributes = null)
+        private TypeInformation GetTypeInformation(
+            Type type,
+            bool getPropertyInfo = false,
+            IEnumerable<Attribute> associatedAttributes = null)
         {
             // This retrieval is implemented as a TryGetValue/TryAdd instead of a GetOrAdd
             // to avoid the performance cost of creating instance delegates
@@ -132,6 +137,14 @@ private TypeInformation GetTypeInformation(Type type, IEnumerable<Attribute> ass
                 typeInfo = CreateTypeInformation(type, associatedAttributes);
                 _typeInfoCache.TryAdd(type, typeInfo);
             }
+
+            if (getPropertyInfo && typeInfo.Properties == null)
+            {
+                var originalTypeInfoValue = typeInfo;
+                typeInfo.Properties = GetInformationOfProperties(type);
+                _typeInfoCache.TryUpdate(type, typeInfo, originalTypeInfoValue);
+            }
+
             return typeInfo;
         }
 
@@ -151,17 +164,6 @@ private TypeInformation CreateTypeInformation(Type type, IEnumerable<Attribute>
                                                     propertyName: null)
             };
 
-            var properties = new Dictionary<string, PropertyInformation>(StringComparer.Ordinal);
-            foreach (var propertyHelper in PropertyHelper.GetProperties(type))
-            {
-                // Avoid re-generating a property descriptor if one has already been generated for the property name
-                if (!properties.ContainsKey(propertyHelper.Name))
-                {
-                    properties.Add(propertyHelper.Name, CreatePropertyInformation(type, propertyHelper));
-                }
-            }
-
-            info.Properties = properties;
             return info;
         }
 
@@ -179,6 +181,22 @@ private PropertyInformation CreatePropertyInformation(Type containerType, Proper
             };
         }
 
+        // This is a safe race because it does not update any shared resource.
+        private Dictionary<string, PropertyInformation> GetInformationOfProperties(Type containerType)
+        {
+            var properties = new Dictionary<string, PropertyInformation>(StringComparer.Ordinal);
+            foreach (var propertyHelper in PropertyHelper.GetProperties(containerType))
+            {
+                // Avoid re-generating a property descriptor if one has already been generated for the property name
+                if (!properties.ContainsKey(propertyHelper.Name))
+                {
+                    properties.Add(propertyHelper.Name, CreatePropertyInformation(containerType, propertyHelper));
+                }
+            }
+
+            return properties;
+        }
+
         private ParameterInformation CreateParameterInfo(
             Type parameterType,
             IEnumerable<object> attributes,

test/Microsoft.AspNet.Mvc.FunctionalTests/ViewComponentTests.cs

@@ -65,6 +65,20 @@ public async Task ViewComponents_SupportsValueType()
             Assert.Equal("10", body.Trim());
         }
 
+        [Fact]
+        public async Task ViewComponents_SupportsEnumerableModel()
+        {
+            var server = TestServer.Create(_provider, _app);
+            var client = server.CreateClient();
+
+            // Act
+            // The invoked ViewComponent has a model which is Enumerable.
+            var body = await client.GetStringAsync("http://localhost/Home/ViewComponentWithEnumerableModel");
+
+            // Assert
+            Assert.Equal("<p>Hello</p><p>World</p><p>Sample</p><p>Test</p>", body.Trim());
+        }
+
         [Theory]
         [InlineData("ViewComponentWebSite.Namespace1.SameName")]
         [InlineData("ViewComponentWebSite.Namespace2.SameName")]

test/WebSites/ViewComponentWebSite/EnumerableViewComponent.cs

@@ -0,0 +1,23 @@
+// 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.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNet.Mvc;
+
+namespace ViewComponentWebSite
+{
+    public class EnumerableViewComponent : ViewComponent
+    {
+        public IViewComponentResult Invoke()
+        {
+            var modelList = new List<SampleModel>()
+            {
+                new SampleModel { Prop1 = "Hello", Prop2 = "World" },
+                new SampleModel { Prop1 = "Sample", Prop2 = "Test" },
+            };
+
+            return View(modelList.Select(e => e));
+        }
+    }
+}

test/WebSites/ViewComponentWebSite/HomeController.cs

@@ -21,5 +21,10 @@ public ViewResult ViewWithIntegerViewComponent()
         {
             return new ViewResult();
         }
+
+        public ViewResult ViewComponentWithEnumerableModel()
+        {
+            return new ViewResult();
+        }
     }
 }

test/WebSites/ViewComponentWebSite/Views/Shared/Components/Enumerable/Default.cshtml

@@ -0,0 +1,3 @@
+@model IEnumerable<SampleModel>
+@foreach (var m in Model)
+{<p>@m.Prop1</p><p>@m.Prop2</p>}

test/WebSites/ViewComponentWebSite/Views/Shared/ViewComponentWithEnumerableModel.cshtml

@@ -0,0 +1 @@
+@Component.Invoke("Enumerable")