using System;

using System.Collections.Generic;

using System.Text;

using System.Xml.Serialization;

using System.IO;

using System.Runtime.Serialization;

using System.Runtime.Serialization.Json;

using System.Reflection;

using System.Linq;

using NUnit.Framework; //NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/58835728/unable-to-deserialize-polymorphic-dictionary-json-due-to-knowntype-type-issu?noredirect=1#comment104043671_58835728

​

    class Program

    {

        static void Main(string[] args)

        {

            var dict = new Dictionary<string, object>()

            {

                { "employee","john" },

                {"sale",new Sale(9,5243) },

                {"restaurant",new Restaurant("Cheese Cake Factory", "New York")},

            };

​

            var settings = new DataContractJsonSerializerSettings

            {

                KnownTypes = new [] { typeof(Sale), typeof(Restaurant) },

            };

            DataContractJsonSerializer js = new DataContractJsonSerializer(typeof(Dictionary<string, object>), settings);  

            var json = DataContractJsonSerializerHelper.ToContractJson(dict, js);

​

            Console.WriteLine(json);

​

            var result = DataContractJsonSerializerHelper.FromContractJson<Dictionary<string, object>>(json, js);

            Console.Write("\n");

​

            Console.WriteLine("Original dictionary:");

            dict.Dump();

​

            Console.WriteLine("Deserialized result:");

            result.Dump();

            Assert.IsTrue(dict.Values.Select(v => v.GetType()).SequenceEqual(result.Values.Select(v => v.GetType())));

        }

    }

​

    [DataContract]

    //[KnownType(typeof(Sale))]

    public class Sale 

    {

        [DataMember(Name = "SaleId")]

        public int SaleId {get; set;}

        [DataMember(Name = "Total")]

        public int Total{ get; set;}

​

        public Sale(int saleid, int total)

        {

            SaleId = saleid;

            Total = total;

        }

​

        public int getTotal()

        {

            return  Total;

        }

    }

​

    [DataContract(Name = "Restaurant", Namespace="")]

    //[KnownType(typeof(Restaurant))]

    public class Restaurant

    {

        [DataMember(EmitDefaultValue = false)]

        public string Name {get; set;}

        [DataMember(EmitDefaultValue = false)]

        public string City{get; set;}

​

        public Restaurant(string name, string city)

        {

            Name = name;

            City = city;

        }

    }

​

​

    public static partial class DataContractJsonSerializerHelper

    {

        private static MemoryStream GenerateStreamFromString(string value)

        {

            return new MemoryStream(Encoding.UTF8.GetBytes(value ?? ""));

        }

​

        public static string ToContractJson<T>(this T obj, DataContractJsonSerializer serializer)

        {

            serializer = serializer ?? new DataContractJsonSerializer(obj == null ? typeof(T) : obj.GetType());

            using (var memory = new MemoryStream())

            {

                serializer.WriteObject(memory, obj);

                memory.Seek(0, SeekOrigin.Begin);

                using (var reader = new StreamReader(memory))

                {

                    return reader.ReadToEnd();

                }

            }

        }

​

        public static T FromContractJson<T>(string json, DataContractJsonSerializer serializer)

        {

            serializer = serializer ?? new DataContractJsonSerializer(typeof(T));

            using (var stream = GenerateStreamFromString(json))

            {

                var obj = serializer.ReadObject(stream);

                return (T)obj;

            }

        }

    }

​