DataContractJsonSerializer在Windows Phone 8.1上永远不会忽略EmitTypeInformation

Question

Windows Universal App 8.1。 DataContractJsonSerializer始终为Windows Phone App 8.1发出派生类的类型信息。它对Windows Store App 8.1的行为正确。

测试代码和结果如下。除了编辑json post序列化之外，还有任何解决方法吗？

using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Json;
using System.Text;

namespace TestEmitTypeInformation
{
    [DataContract]
    public class DataContractBase
    {
        [DataMember]
        public string BaseString { get; set; }
    }

    [DataContract]
    public class DataContractDerived : DataContractBase
    {
        [DataMember]
        public string DerivedString { get; set; }
    }

    public class DataContractTest
    {

        public static void SerializeTestAll()
        {
            var test = new DataContractTest();
            test.SerializeTest(System.Runtime.Serialization.EmitTypeInformation.Always);
            test.SerializeTest(System.Runtime.Serialization.EmitTypeInformation.AsNeeded);
            test.SerializeTest(System.Runtime.Serialization.EmitTypeInformation.Never);
        }

        public void SerializeTest(EmitTypeInformation emitTypeInfo)
        {
            var testObject = new DataContractDerived() {  BaseString="Base", DerivedString="Derived" };

            using (MemoryStream memStream = new MemoryStream())
            {
                var serializationSettings =
                    new DataContractJsonSerializerSettings()
                    {
                        EmitTypeInformation = emitTypeInfo,
                        KnownTypes = new Type[] { typeof(DataContractDerived) }
                    };
                DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(DataContractBase), serializationSettings);
                ser.WriteObject(memStream, testObject);

                memStream.Position = 0;
                string jsonContent = new StreamReader(memStream).ReadToEnd();

                Debug.WriteLine("Result: EmitTypeInformation {0}\n{1}", emitTypeInfo, jsonContent);
            }
        }
    }
}

调用DataContractTest.SerializeTestAll（）的结果是： - Windows 8.1

Result: EmitTypeInformation Always
{"__type":"DataContractDerived:#TestEmitTypeInformation","BaseString":"Base","DerivedString":"Derived"}
Result: EmitTypeInformation AsNeeded
{"__type":"DataContractDerived:#TestEmitTypeInformation","BaseString":"Base","DerivedString":"Derived"}
Result: EmitTypeInformation Never
{"BaseString":"Base","DerivedString":"Derived"}

Windows Phone 8.1

Result: EmitTypeInformation Always
{"__type":"DataContractDerived:#TestEmitTypeInformation","BaseString":"Base","DerivedString":"Derived"}
Result: EmitTypeInformation AsNeeded
{"__type":"DataContractDerived:#TestEmitTypeInformation","BaseString":"Base","DerivedString":"Derived"}
Result: EmitTypeInformation Never
{"__type":"DataContractDerived:#TestEmitTypeInformation","BaseString":"Base","DerivedString":"Derived"}