[Fork] questions/48791322/how-to-ignore-empty-arrays-using-jsonconvert-deserializeobject

CSharp · Console

/Program.cs

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/48791322/how-to-ignore-empty-arrays-using-jsonconvert-deserializeobject
    public class IgnoreUnexpectedArraysConverter<T> : IgnoreUnexpectedArraysConverterBase
    {
        public override bool CanConvert(Type objectType)
        {
            return typeof(T).IsAssignableFrom(objectType);
        }
    }

    public class IgnoreUnexpectedArraysConverter : IgnoreUnexpectedArraysConverterBase
    {
        readonly IContractResolver resolver;

        public IgnoreUnexpectedArraysConverter(IContractResolver resolver)
        {
            if (resolver == null)
                throw new ArgumentNullException();
            this.resolver = resolver;
        }

        public override bool CanConvert(Type objectType)
        {
            if (objectType.IsPrimitive || objectType == typeof(string))
                return false;
            return resolver.ResolveContract(objectType) is JsonObjectContract;
        }
    }

    public abstract class IgnoreUnexpectedArraysConverterBase : JsonConverter
    {
        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            var contract = serializer.ContractResolver.ResolveContract(objectType);
            if (!(contract is JsonObjectContract))
            {
                throw new JsonSerializationException(string.Format("{0} is not a JSON object", objectType));
            }

            do
            {
                if (reader.TokenType == JsonToken.Null)
                    return null;
                else if (reader.TokenType == JsonToken.Comment)
                    continue;
				else if (reader.TokenType == JsonToken.StartArray)
				{
					var array = JArray.Load(reader);
					if (array.Count > 0)
						throw new JsonSerializationException(string.Format("Array was not empty."));
					return existingValue ?? contract.DefaultCreator();
				}					
                else if (reader.TokenType == JsonToken.StartObject)
                {
                    // Prevent infinite recursion by using Populate()
                    existingValue = existingValue ?? contract.DefaultCreator();
                    serializer.Populate(reader, existingValue);
                    return existingValue;
                }
                else
                {
                    throw new JsonSerializationException(string.Format("Unexpected token {0}", reader.TokenType));
                }
            }
            while (reader.Read());
            throw new JsonSerializationException("Unexpected end of JSON.");
        }

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

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            throw new NotImplementedException();
        }
    }

    public class Item
    {
        public string category_name { get; set; }
        public string category_id { get; set; }
        public bool is_primary { get; set; }
    }

    public class Categories
    {
        public int count { get; set; }
        public List<Item> items { get; set; }
    }

    public class Venue
    {
        public int venue_id { get; set; }
        public string venue_name { get; set; }
        public string venue_slug { get; set; }
        public string primary_category { get; set; }
        public string parent_category_id { get; set; }
        public Categories categories { get; set; }
        public bool is_verified { get; set; }
    }

    public class Rootobject
    {
        public Venue venue { get; set; }
    }

    class TestClass
    {
        public static void Test()
        {
            foreach (var json in GetJson())
            {
                Test<Rootobject>(json);
            }
        }

        public static void Test<Rootobject>(string jsonString)
        {
            var resolver = new DefaultContractResolver(); // Cache for performance
            var settings = new JsonSerializerSettings
            {
                ContractResolver = resolver,
                Converters = { new IgnoreUnexpectedArraysConverter(resolver) },
            };
            var userInfo = JsonConvert.DeserializeObject<Rootobject>(jsonString, settings);
            var json2 = JsonConvert.SerializeObject(userInfo, Formatting.Indented, settings);
            Console.WriteLine(json2);
        }

        static IEnumerable<string> GetJson()
        {
            var json = new[]
            {
                @"
{
   ""venue"":{
      ""venue_id"":696895,
      ""venue_name"":""Blackfinn Ameripub"",
      ""venue_slug"":""blackfinn-ameripub"",
      ""primary_category"":""Food"",
      ""parent_category_id"":""4d4b7105d754a06374d81259"",
      ""categories"":{
         ""count"":1,
         ""items"":[
            {
               ""category_name"":""American Restaurant"",
               ""category_id"":""4bf58dd8d48988d14e941735"",
               ""is_primary"":true
            }
         ]
      },
      ""is_verified"":false
   }
}",
                @"
{
   ""venue"":[]
}",
                @"
{
   ""venue"":/* Some comments to mess you up */ []
}",

                @"
{
   ""venue"":{
      ""venue_id"":696895,
      ""venue_name"":""Blackfinn Ameripub"",
      ""venue_slug"":""blackfinn-ameripub"",
      ""primary_category"":""Food"",
      ""parent_category_id"":""4d4b7105d754a06374d81259"",
      ""categories"": [],
      ""is_verified"":false
   }
}
",
				@"
{
   ""venue"":{
      ""venue_id"":696895,
      ""venue_name"":""Blackfinn Ameripub"",
      ""venue_slug"":""blackfinn-ameripub"",
      ""primary_category"":""Food"",
      ""parent_category_id"":""4d4b7105d754a06374d81259"",
      ""categories"":{
         ""count"":1,
         ""items"":[
             /* Some comments to mess you up */ [] 
         ]
      },
      ""is_verified"":false
   }
}"
			};
            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");
        }
    }