-Fixed invalid Required.Always error with constructor property name casing

-Fixed empty string coerce check with Required.Always and constructor

Src/Newtonsoft.Json.Tests/Serialization/JsonSerializerTest.cs

@@ -95,6 +95,36 @@ namespace Newtonsoft.Json.Tests.Serialization
     [TestFixture]
     public class JsonSerializerTest : TestFixtureBase
     {
+        [Test]
+        public void CaseInsensitiveRequiredPropertyConstructorCreation()
+        {
+            FooRequired foo1 = new FooRequired(new[] { "A", "B", "C" });
+            string json = JsonConvert.SerializeObject(foo1);
+
+            StringAssert.AreEqual(@"{""Bars"":[""A"",""B"",""C""]}", json);
+
+            FooRequired foo2 = JsonConvert.DeserializeObject<FooRequired>(json);
+            Assert.AreEqual(foo1.Bars.Count, foo2.Bars.Count);
+            Assert.AreEqual(foo1.Bars[0], foo2.Bars[0]);
+            Assert.AreEqual(foo1.Bars[1], foo2.Bars[1]);
+            Assert.AreEqual(foo1.Bars[2], foo2.Bars[2]);
+        }
+
+        public class FooRequired
+        {
+            [JsonProperty(Required = Required.Always)]
+            public List<string> Bars { get; private set; }
+
+            public FooRequired(IEnumerable<string> bars)
+            {
+                Bars = new List<string>();
+                if (bars != null)
+                {
+                    Bars.AddRange(bars);
+                }
+            }
+        }
+
         [Test]
         public void CoercedEmptyStringWithRequired()
         {
@@ -104,6 +134,15 @@ namespace Newtonsoft.Json.Tests.Serialization
             }, "Required property 'RequiredProperty' expects a value but got null. Path '', line 1, position 21.");
         }
 
+        [Test]
+        public void CoercedEmptyStringWithRequiredConstructor()
+        {
+            ExceptionAssert.Throws<JsonSerializationException>(() =>
+            {
+                JsonConvert.DeserializeObject<FooRequired>("{Bars:''}");
+            }, "Required property 'Bars' expects a value but got null. Path '', line 1, position 9.");
+        }
+
         public class Binding
         {
             [JsonProperty(Required = Required.Always)]

Src/Newtonsoft.Json/Serialization/JsonSerializerInternalReader.cs

@@ -1661,9 +1661,28 @@ namespace Newtonsoft.Json.Serialization
                 if (propertiesPresence != null)
                 {
                     // map from creator property to normal property
-                    JsonProperty presenceProperty = propertiesPresence.Keys.FirstOrDefault(p => p.PropertyName == property.PropertyName);
+                    JsonProperty presenceProperty = propertiesPresence.Keys.ForgivingCaseSensitiveFind(p => p.PropertyName, property.PropertyName);
                     if (presenceProperty != null)
-                        propertiesPresence[presenceProperty] = (propertyValue.Value == null) ? PropertyPresence.Null : PropertyPresence.Value;
+                    {
+                        object v = propertyValue.Value;
+                        PropertyPresence propertyPresence;
+                        if (v == null)
+                        {
+                            propertyPresence = PropertyPresence.Null;
+                        }
+                        else if (v is string)
+                        {
+                            propertyPresence = CoerceEmptyStringToNull(property.PropertyType, property.PropertyContract, (string)v)
+                                ? PropertyPresence.Null
+                                : PropertyPresence.Value;
+                        }
+                        else
+                        {
+                            propertyPresence = PropertyPresence.Value;
+                        }
+
+                        propertiesPresence[presenceProperty] = propertyPresence;
+                    }
                 }
             }