using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

// https://stackoverflow.com/questions/46047308/how-to-add-metadata-to-describe-which-properties-are-dates-in-json-net

​

​

    public class Example

    {

        public string NotADate { get; set; }

        public DateTime ADate { get; set; }

        public DateTime AnotherDate { get; set; }

    }

​

    public class RootObject

    {

        public int Id { get; set; }

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        public DateTime? DateTime { get; set; }

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        public Example Example { get; set; }

    }

​

    class TestClass

    {

        public static void Test()

        {

            TestExample();

            TestAndValidate();

        }

​

        static void TestExample()

        {

            var example = new Example

            {

                ADate = DateTime.Parse("2017-04-23T18:25:43.511Z", CultureInfo.InvariantCulture),

                AnotherDate = DateTime.Parse("2017-04-23T18:25:43.511Z", CultureInfo.InvariantCulture),

                NotADate = "a value",

            };

​

            var settings = new JsonSerializerSettings

            {

                ContractResolver = new ConfigurableContractResolver

                {

                    // Here I am using CamelCaseNamingStrategy as is shown in your JSON.

                    // If you don't want camel case, leave NamingStrategy null.

                    //NamingStrategy = new CamelCaseNamingStrategy(),

                    // No NamingStrategy available on dotnetfiddle.net which is still running Json.NET 6.0!

                }.Configure((s, e) => { e.Contract.AddDateProperties(); }),

            };

​

            var json = JsonConvert.SerializeObject(example, Formatting.Indented, settings);

​

            Console.WriteLine(string.Format("Serialized {0}:", example));

            Console.WriteLine(json);

        }

​

        static void TestAndValidate()

        {

            var settings = new JsonSerializerSettings

            {

                ContractResolver = new ConfigurableContractResolver

                {

                    //NamingStrategy = new CamelCaseNamingStrategy(),

                }.Configure((s, e) => { e.Contract.AddDateProperties(); }),

                TypeNameHandling = TypeNameHandling.All,

                TypeNameAssemblyFormat = FormatterAssemblyStyle.Full,

            };

​

            var root = new RootObject

            {

                Id = 101,

                DateTime = DateTime.Parse("2016-08-02 05:49:11.000Z", CultureInfo.InvariantCulture),

                Example = new Example

                {

                    ADate = DateTime.Parse("2017-04-23T18:25:43.511Z", CultureInfo.InvariantCulture),

                    AnotherDate = DateTime.Parse("2017-04-23T18:25:43.511Z", CultureInfo.InvariantCulture),

                    NotADate = "a value",

                }

            };

​

            var json = JsonConvert.SerializeObject(root, Formatting.Indented, settings);

​

            Console.WriteLine(string.Format("Serialized {0}", root));

            Console.WriteLine(json);

​

            var root2 = JsonConvert.DeserializeObject<RootObject>(json, settings);

​

            var json2 = JsonConvert.SerializeObject(root2, Formatting.Indented, settings);

​

            Assert.IsTrue(json == json2);

​

            Assert.IsTrue(JToken.DeepEquals(JToken.Parse(json).SelectToken("_date_properties_"), JToken.Parse(@"[""DateTime""]")));

            Assert.IsTrue(JToken.DeepEquals(JToken.Parse(json).SelectToken("Example._date_properties_"), JToken.Parse(@"[""ADate"", ""AnotherDate""]")));

​

            try

            {

                ((ConfigurableContractResolver)settings.ContractResolver).ContractCreated += (o, e) => { };

                Assert.IsTrue(false, "Adding a ContractCreated handler here should have failed!");

            }

            catch (InvalidOperationException ex)

            {

                Console.WriteLine(string.Format("Caught expected exception \"{0}\" when trying to add a ContractCreated handler after the first contract is generated.", ex.Message));

            }

​

            Console.WriteLine("All tests passed.");

        }

    }

​

    public class ConfigurableContractResolver : DefaultContractResolver

    {

        readonly object contractCreatedPadlock = new object();

        event EventHandler<ContractCreatedEventArgs> contractCreated;

        int contractCount = 0;

​

        void OnContractCreated(JsonContract contract, Type objectType)

        {

            EventHandler<ContractCreatedEventArgs> created;

            lock (contractCreatedPadlock)

            {

                contractCount++;

                created = contractCreated;

            }

            if (created != null)

            {

                created(this, new ContractCreatedEventArgs(contract, objectType));

            }

        }

​

        public event EventHandler<ContractCreatedEventArgs> ContractCreated

        {

            add

            {

                lock (contractCreatedPadlock)

                {

                    if (contractCount > 0)

                    {

                        throw new InvalidOperationException("ContractCreated events cannot be added after the first contract is generated.");

                    }

                    contractCreated += value;

                }

            }

            remove

            {

                lock (contractCreatedPadlock)

                {

                    if (contractCount > 0)

                    {

                        throw new InvalidOperationException("ContractCreated events cannot be removed after the first contract is generated.");

                    }

                    contractCreated -= value;

                }

            }  

        }

​

        protected override JsonContract CreateContract(Type objectType)

        {

            var contract = base.CreateContract(objectType);

            OnContractCreated(contract, objectType);

            return contract;

        }

    }

​

    public class ContractCreatedEventArgs : EventArgs

    {

        public JsonContract Contract { get; private set; }

        public Type ObjectType { get; private set; }

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        public ContractCreatedEventArgs(JsonContract contract, Type objectType)

        {

            this.Contract = contract;

            this.ObjectType = objectType;

        }

    }

​

    public static class ConfigurableContractResolverExtensions

    {

        public static ConfigurableContractResolver Configure(this ConfigurableContractResolver resolver, EventHandler<ContractCreatedEventArgs> handler)

        {

            if (resolver == null || handler == null)

                throw new ArgumentNullException();

            resolver.ContractCreated += handler;

            return resolver;

        }

    }

​

    public static class JsonContractExtensions

    {

        const string DatePropertiesName = "_date_properties_";

​

        public static void AddDateProperties(this JsonContract contract)

        {

            var objectContract = contract as JsonObjectContract;

            if (objectContract == null)

                return;

            var properties = objectContract.Properties.Where(p => p.PropertyType == typeof(DateTime) || p.PropertyType == typeof(DateTime?)).ToList();

            if (properties.Count > 0)

            {

                var property = new JsonProperty

                {

                    DeclaringType = contract.UnderlyingType,

                    PropertyName = DatePropertiesName,

                    UnderlyingName = DatePropertiesName,

                    PropertyType = typeof(string[]),

                    ValueProvider = new FixedValueProvider(properties.Select(p => p.PropertyName).ToArray()),

                    AttributeProvider = new NoAttributeProvider(),

                    Readable = true,

                    Writable = false,

                    // Ensure // Ensure PreserveReferencesHandling and TypeNameHandling do not apply to the synthetic property.

                    ItemIsReference = false, 

                    TypeNameHandling = TypeNameHandling.None,

                };

                objectContract.Properties.Insert(0, property);

            }

        }

​

        class FixedValueProvider : IValueProvider

        {

            readonly object properties;

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            public FixedValueProvider(object value)

            {

                this.properties = value;

            }

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            #region IValueProvider Members

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            public object GetValue(object target)

            {

                return properties;

            }

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            public void SetValue(object target, object value)

            {

                throw new NotImplementedException("SetValue not implemented for fixed properties; set JsonProperty.Writable = false.");

            }

​

            #endregion

        }

​

        class NoAttributeProvider : IAttributeProvider

        {

            #region IAttributeProvider Members

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            public IList<Attribute> GetAttributes(Type attributeType, bool inherit) { return new Attribute[0]; }

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            public IList<Attribute> GetAttributes(bool inherit) { return new Attribute[0]; }

​

            #endregion

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: " + Environment.Version);

            Console.WriteLine("Json.NET version: " + typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​

    public class AssertionFailedException : System.Exception

    {

        public AssertionFailedException() : base() { }

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        public AssertionFailedException(string s) : base(s) { }

    }

​

    public static class Assert

    {

        public static void IsTrue(bool value)

        {

            IsTrue(value, "failed");

        }

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        public static void IsTrue(bool value, string message)

        {

            if (value == false)

                throw new AssertionFailedException(message ?? "failed");

        }

    }

​