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/49109312/c-sharp-newtonsoft-json-deserializeobject-issue

    public class Root

    {

        [JsonConverter(typeof(TolerantObjectCollectionConverter<FreeGifts>))]

        public List<FreeGifts> FreeGifts { get; set; }

    }

​

    public class FreeGifts

    {

        [JsonConverter(typeof(SingleOrArrayConverter<FreeGift>))]

        public List<FreeGift> FreeGift { get; set; }

    }

​

    public class FreeGift

    {

        public string SKU { get; set; }

    }

​

    class SingleOrArrayConverter<T> : JsonConverter

    {

        // Taken from the answer to 

        // https://stackoverflow.com/questions/18994685/how-to-handle-both-a-single-item-and-an-array-for-the-same-property-using-json-n

        // https://stackoverflow.com/a/18997172

        // by Brian Rogers

        public override bool CanConvert(Type objectType)

        {

            return (objectType == typeof(List<T>));

        }

​

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

        {

            var tokenType = reader.SkipComments().TokenType;

            if (tokenType == JsonToken.Null)

                return null;

            var list = existingValue as List<T> ?? new List<T>();

            if (tokenType == JsonToken.StartArray)

            {

                serializer.Populate(reader, list);

            }

            else

            {

                list.Add(serializer.Deserialize<T>(reader));

            }

            return list;

        }

​

        public override bool CanWrite { get { return false; } }

​

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

        {

            throw new NotImplementedException();

        }

    }

​

    public class TolerantObjectCollectionConverter<TItem> : JsonConverter

    {

        // Taken from the answer to 

        // https://stackoverflow.com/questions/49030516/how-can-i-ignore-a-blank-array-inside-an-array-of-json-objects-while-deserializi

        // https://stackoverflow.com/a/49078620/

​

        public override bool CanConvert(Type objectType)

        {

            return !objectType.IsArray && objectType != typeof(string) && typeof(ICollection<TItem>).IsAssignableFrom(objectType);

        }

​

        public override bool CanWrite { get { return false; } }

​

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

        {

            throw new NotImplementedException();

        }

​

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

        {

            // Get contract information

            var contract = serializer.ContractResolver.ResolveContract(objectType) as JsonArrayContract;

            if (contract == null || contract.IsMultidimensionalArray || objectType.IsArray)

                throw new JsonSerializationException(string.Format("Invalid array contract for {0}", objectType));

​

            // Process the first token

            var tokenType = reader.SkipComments().TokenType;

            if (tokenType == JsonToken.Null)

                return null;

            if (tokenType != JsonToken.StartArray)

                throw new JsonSerializationException(string.Format("Expected {0}, encountered {1} at path {2}", JsonToken.StartArray, reader.TokenType, reader.Path));

​

            // Allocate the collection

            var collection = existingValue as ICollection<TItem> ?? (ICollection<TItem>)contract.DefaultCreator();

​

            // Process the collection items

            while (reader.Read())

            {

                switch (reader.TokenType)

                {

                    case JsonToken.EndArray:

                        return collection;

​

                    case JsonToken.StartObject:

                    case JsonToken.Null:

                        collection.Add(serializer.Deserialize<TItem>(reader));

                        break;

​

                    default:

                        reader.Skip();

                        break;

                }

            }

            // Should not come here.

            throw new JsonSerializationException("Unclosed array at path: " + reader.Path);

        }

    }

​

    public static partial class JsonExtensions

    {

        public static JsonReader SkipComments(this JsonReader reader)

        {

            while (reader.TokenType == JsonToken.Comment && reader.Read())

                ;

            return reader;

        }

    }

​

    static class TestClass

    {

        public static void Test()

        {

            foreach (var json in GetJson())

            {

                Test(json);

            }

            Console.WriteLine("\nDone.");

        }

​

        static void Test(string json)

        {

            var root = JsonConvert.DeserializeObject<Root>(json);

​

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

​

            var count1 = JToken.Parse(json).SelectTokens("..SKU").Count();

            var count2 = (root.FreeGifts ?? Enumerable.Empty<FreeGifts>()).SelectMany(f => f.FreeGift ?? Enumerable.Empty<FreeGift>()).Count();

            Assert.IsTrue(count1 == count2);

​

            Console.WriteLine("\nRe-serialized JSON:");

            Console.WriteLine(json2);

        }

​

        static IEnumerable<string> GetJson()

        {

            var json = new[]

            {

                @"    {

        ""FreeGifts"": [{

            ""FreeGift"": [{

                    ""SKU"": ""BOWS-SMALL-ALFIE""

                },

                {

                    ""SKU"": ""BOWS-LARGE-ALONZO""

                },

                {

                    ""SKU"": ""BOWS-LARGE-CLANCY""

                },

                {

                    ""SKU"": ""BOWS-SMALL-ALVIN""

                },

                {

                    ""SKU"": ""BOWS-SMALL-CLARK""

                }

            ]

        }]

    }",

            @"    {

        ""FreeGifts"": [{

            ""FreeGift"": {

                ""SKU"": ""BOWS-SMALL-ALVIN""

            }

        }]

    }",

            @"    {

        ""FreeGifts"": [

            """"

        ]

    }",

            };

            return json;

        }

    }

​

    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() { }

​

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

    }

​

    public static class Assert

    {

        public static void IsTrue(bool value)

        {

            IsTrue(value, "failed");

        }

​

        public static void IsTrue(bool value, string message)

        {

            if (value == false)

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

        }

    }

​