using System;

using System.Linq;

using System.Collections.Generic;

using Newtonsoft.Json;

​

public class StringsWithoutNonprintablesConverter : JsonConverter<string>

{

    public override string ReadJson(JsonReader reader, Type objectType, string existingValue, bool hasExistingValue, JsonSerializer serializer)

    {

        if (reader.TokenType != JsonToken.String)

            throw new System.IO.InvalidDataException("Json data is not a string value");

​

        var s = (string) reader.Value;

​

        return (s.Any(char.IsControl)) ? new string(s.Where(c => !char.IsControl(c)).ToArray()) : s;

    }

​

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

    {

        writer.WriteValue(value);

    }

}

​

​

​

public class Program

{

    public static void Main()

    {

        var json =

@"{

    ""1"":  ""\t\tSay \""Hello\""\n\u0010\n"",

    ""2"":  ""Something with non-printable\ncontrol\tchar sequences"",

    ""3"":  ""Something with printable control ch\u0061r sequences"",

    ""4"":  ""Something with both non-printable and printable\u0009control ch\u0061r sequences""

}";

        Console.WriteLine("The source json:");

        Console.WriteLine(json);

        Console.WriteLine();

        Console.WriteLine("---------------------------------------------");

        Console.WriteLine("The deserialization result without filtering:");

        var dict = JsonConvert.DeserializeObject <Dictionary<string, string>>(json);

        foreach (var kvp in dict)

            Console.WriteLine($"{kvp.Key}:  {kvp.Value}");

​

        Console.WriteLine();

        Console.WriteLine("---------------------------------------------");

        Console.WriteLine("The deserialization result with filtering:");

        JsonConvert.DefaultSettings = () => new JsonSerializerSettings

        {

            Converters = new[] { new StringsWithoutNonprintablesConverter() }

        };

        dict = JsonConvert.DeserializeObject <Dictionary<string, string>>(json);

        foreach (var kvp in dict)

            Console.WriteLine($"{kvp.Key}:  {kvp.Value}");

    }

}