From a04f5cba9ab36ecd01d2616f13dcda2bdeed8514 Mon Sep 17 00:00:00 2001
From: Ben Adams <thundercat@illyriad.co.uk>
Date: Wed, 28 Sep 2016 23:23:17 +0100
Subject: [PATCH] Remove ViewDataEvaluator.GetPropertyValue Closure (#5325)

- part of #3918
---
 .../ViewFeatures/ViewDataEvaluator.cs         |  2 +-
 .../ViewFeatures/ViewDataInfo.cs              | 40 +++++++++++++++++--
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/ViewDataEvaluator.cs b/src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/ViewDataEvaluator.cs
index ed3ccbe49a..e52b336458 100644
--- a/src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/ViewDataEvaluator.cs
+++ b/src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/ViewDataEvaluator.cs
@@ -203,7 +203,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
                 return null;
             }
 
-            return new ViewDataInfo(container, propertyInfo, () => propertyInfo.GetValue(container));
+            return new ViewDataInfo(container, propertyInfo);
         }
 
         private struct ExpressionPair
diff --git a/src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/ViewDataInfo.cs b/src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/ViewDataInfo.cs
index c43eaa68c4..62e273a4ae 100644
--- a/src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/ViewDataInfo.cs
+++ b/src/Microsoft.AspNetCore.Mvc.ViewFeatures/ViewFeatures/ViewDataInfo.cs
@@ -8,6 +8,8 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
 {
     public class ViewDataInfo
     {
+        private static readonly Func<object> _propertyInfoResolver = () => null;
+
         private object _value;
         private Func<object> _valueAccessor;
 
@@ -15,6 +17,8 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
         /// Initializes a new instance of the <see cref="ViewDataInfo"/> class with info about a
         /// <see cref="ViewDataDictionary"/> lookup which has already been evaluated.
         /// </summary>
+        /// <param name="container">The <see cref="object"/> that <paramref name="value"/> was evaluated from.</param>
+        /// <param name="value">The evaluated value.</param>
         public ViewDataInfo(object container, object value)
         {
             Container = container;
@@ -23,8 +27,25 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ViewDataInfo"/> class with info about a
-        /// <see cref="ViewDataDictionary"/> lookup which is evaluated when <see cref="Value"/> is read.
+        /// <see cref="ViewDataDictionary"/> lookup which is evaluated when <see cref="Value"/> is read. 
+        /// It uses <see cref="System.Reflection.PropertyInfo.GetValue(object)"/> on <paramref name="propertyInfo"/> 
+        /// passing parameter <paramref name="container"/> to lazily evaluate the value.
         /// </summary>
+        /// <param name="container">The <see cref="object"/> that <see cref="Value"/> will be evaluated from.</param>
+        /// <param name="propertyInfo">The <see cref="PropertyInfo"/> that will be used to evalute <see cref="Value"/>.</param>
+        public ViewDataInfo(object container, PropertyInfo propertyInfo)
+            : this(container, propertyInfo, _propertyInfoResolver)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ViewDataInfo"/> class with info about a
+        /// <see cref="ViewDataDictionary"/> lookup which is evaluated when <see cref="Value"/> is read.
+        /// It uses <paramref name="valueAccessor"/> to lazily evaluate the value.
+        /// </summary>
+        /// <param name="container">The <see cref="object"/> that has the <see cref="Value"/>.</param>
+        /// <param name="propertyInfo">The <see cref="PropertyInfo"/> that represents <see cref="Value"/>'s property.</param>
+        /// <param name="valueAccessor"></param>
         public ViewDataInfo(object container, PropertyInfo propertyInfo, Func<object> valueAccessor)
         {
             Container = container;
@@ -42,8 +63,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
             {
                 if (_valueAccessor != null)
                 {
-                    _value = _valueAccessor();
-                    _valueAccessor = null;
+                    ResolveValue();
                 }
 
                 return _value;
@@ -54,5 +74,19 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
                 _valueAccessor = null;
             }
         }
+
+        private void ResolveValue()
+        {
+            if (ReferenceEquals(_valueAccessor, _propertyInfoResolver))
+            {
+                _value = PropertyInfo.GetValue(Container);
+            }
+            else
+            {
+                _value = _valueAccessor();
+            }
+
+            _valueAccessor = null;
+        }
     }
 }