-Fixed serializing types with hidden properties

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

@@ -5112,6 +5112,23 @@ keyword such as type of business.""
       Assert.AreEqual(d1.Count, d2.Count);
       Assert.AreEqual(d1[0], d2[0]);
     }
+
+    [Test]
+    public void SerializeInheritanceHierarchyWithDuplicateProperty()
+    {
+      Bb b = new Bb();
+      b.no = true;
+      Aa a = b;
+      a.no = int.MaxValue;
+
+      string json = JsonConvert.SerializeObject(b);
+
+      Assert.AreEqual(@"{""no"":true}", json);
+
+      Bb b2 = JsonConvert.DeserializeObject<Bb>(json);
+
+      Assert.AreEqual(true, b2.no);
+    }
   }
 
   public class DecimalTestClass
@@ -5146,6 +5163,16 @@ keyword such as type of business.""
     public Uri Uri { get; set; }
   }
 
+  class Aa
+  {
+    public int no;
+  }
+
+  class Bb : Aa
+  {
+    public bool no;
+  }
+
 #if !(NET35 || NET20 || SILVERLIGHT || WINDOWS_PHONE)
   [JsonObject(MemberSerialization.OptIn)]
   public class GameObject

Src/Newtonsoft.Json/Serialization/DefaultContractResolver.cs

@@ -808,6 +808,7 @@ namespace Newtonsoft.Json.Serialization
     {
       JsonProperty property = new JsonProperty();
       property.PropertyType = ReflectionUtils.GetMemberUnderlyingType(member);
+      property.DeclaringType = member.DeclaringType;
       property.ValueProvider = CreateMemberValueProvider(member);
 
       bool allowNonPublicAccess;

Src/Newtonsoft.Json/Serialization/JsonProperty.cs

@@ -41,6 +41,12 @@ namespace Newtonsoft.Json.Serialization
     /// <value>The name of the property.</value>
     public string PropertyName { get; set; }
 
+    /// <summary>
+    /// Gets or sets the type that declared this property.
+    /// </summary>
+    /// <value>The type that declared this property.</value>
+    public Type DeclaringType { get; set; }
+
     /// <summary>
     /// Gets or sets the order of serialization and deserialization of a member.
     /// </summary>

Src/Newtonsoft.Json/Serialization/JsonPropertyCollection.cs

@@ -73,12 +73,30 @@ namespace Newtonsoft.Json.Serialization
 
         JsonProperty existingProperty = this[property.PropertyName];
 
-        if (!existingProperty.Ignored)
-          throw new JsonSerializationException(
-            "A member with the name '{0}' already exists on '{1}'. Use the JsonPropertyAttribute to specify another name.".FormatWith(CultureInfo.InvariantCulture, property.PropertyName, _type));
+        if (existingProperty.Ignored)
+        {
+          // remove ignored property so it can be replaced in collection
+          Remove(existingProperty);
+          return;
+        }
 
-        // remove ignored property so it can be replaced in collection
-        Remove(existingProperty);
+        if (property.DeclaringType != null && existingProperty.DeclaringType != null)
+        {
+          if (property.DeclaringType.IsSubclassOf(existingProperty.DeclaringType))
+          {
+            // current property is on a derived class and hides the existing
+            Remove(existingProperty);
+            return;
+          }
+          if (existingProperty.DeclaringType.IsSubclassOf(property.DeclaringType))
+          {
+            // current property is hidden by the existing so don't add it
+            return;
+          }
+        }
+
+        throw new JsonSerializationException(
+          "A member with the name '{0}' already exists on '{1}'. Use the JsonPropertyAttribute to specify another name.".FormatWith(CultureInfo.InvariantCulture, property.PropertyName, _type));
       }
 
       Add(property);