Json对Tuples反序列化有问题吗？

Question

I have a class I use for configuration that holds a 3 tuple of all integers.

public class Configuration
{
    public List<Tuple<int, int, int>> MyThreeTuple { get; set; }

    public Configuration()
    {
        MyThreeTuple = new List<Tuple<int, int, int>>();
        MyThreeTuple.Add(new Tuple<int, int, int>(-100, 20, 501));
        MyThreeTuple.Add(new Tuple<int, int, int>(100, 20, 864));
        MyThreeTuple.Add(new Tuple<int, int, int>(500, 20, 1286));
    }
}

This class is serialized into Json with System.Web.Script.Serialization as such

JavaScriptSerializer jsonSerializer = new JavaScriptSerializer();
String configJson = jsonSerializer.Serialize(config);
File.WriteAllText(configPath, configJson);

and then deserialized when the application is launched

String configJson = File.ReadAllText(configPath);
JavaScriptSerializer jsonSerializer = new JavaScriptSerializer(); 
object jsonObject = jsonSerializer.Deserialize(configJson, typeof(ApplicationConfiguration));
appConfig = (Configuration)jsonObject;

My issue is that whenever I go to deserialize the Json an exception is thrown

System.MissingMethodException in System.Web.Extensions.dll 

With the message

No parameterless constructor defined for type of `System.Tuple`3 ....

This is what the produced Json for the tuple looks like

"MyThreeTuple":
 [
    {"Item1":-100,"Item2":20,"Item3":501},
    {"Item1":100,"Item2":20,"Item3":864},
    {"Item1":500,"Item2":20,"Item3":1286}
 ]

Any idea how to solve this problem?

EDIT:

As other have suggested I tried out JSon.NET and it seems to work to deserialize the json. Though I have found an odd quirk.

So the constructor for my Configuration class fills in default values for the configuration. Specifically what is given in the code above. I have found that I can serialize the configuration with different values, but when deserialized, the default values are also loaded to the List<Tuple<>> .

I assume the Json.Net gets around the issue of Tuple not having a parameterless constructor by first instantiating Configuration and then setting its values.

It seems to be instantiating the class, then List.Add ing the Tuple s it finds in the json to the list. Instead of clearing the list then adding what it finds.

Is there an option in JSon.Net to solve this issue?

Answer 1

The reason why you got this error because JavascriptSerializer requires a public parameter-less constructor which is not the case for Tuple because it's an immutable

take a look here http://json.codeplex.com/ for full comparison between javascriptserializer and json.net

Even microsoft states in the documentation

Json.NET should be used serialization and deserialization. Provides serialization and deserialization functionality for AJAX-enabled applications.

here an example on how you can easily use JsonConvert to achieve this

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Newtonsoft.Json;

namespace ConsoleApplication25
{
    class Program
    {
        static void Main(string[] args)
        {
            Configuration configuration = new Configuration();
            string configJson = JsonConvert.SerializeObject(configuration);
            File.WriteAllText(configPath, configJson);
            //Deserialize the  content after you read your file in string 

             var   configurationDeserialized = JsonConvert.DeserializeObject<Configuration>(configJson); 



        }
    }
}

public class Configuration
{
     [JsonIgnore]
    public List<Tuple<int, int, int>> MyThreeTuple { get; set; }

    public Configuration()
    {
        MyThreeTuple = new List<Tuple<int, int, int>>();
        MyThreeTuple.Add(new Tuple<int, int, int>(-100, 20, 501));
        MyThreeTuple.Add(new Tuple<int, int, int>(100, 20, 864));
        MyThreeTuple.Add(new Tuple<int, int, int>(500, 20, 1286));
    }
}

Answer 2

You can resolve using Newtonsoft.Json

1. Install Newtonsoft.Json using nuget ( https://www.nuget.org/packages/Newtonsoft.Json/ )

Serialize :

var myObject = new Configuration();
var objString = JsonConvert.SerializeObject(myObject);

Deserialize:

 var result = JsonConvert.DeserializeObject(objString, typeof(Configuration)); 

Or

var result = JsonConvert.DeserializeObject<Configuration>(objString);

Answer 3

Just for completeness, I wanted to point out that it is possible to deserialize a Tuple<int, int, int> using the JavaScriptSerializer , but you need a JavaScriptConverter to do it. The converter handles instantiating the Tuple from the values in the JSON, thus avoiding the exception.

class ThreeTupleConverter : JavaScriptConverter
{
    public override IEnumerable<Type> SupportedTypes
    {
        get { return new List<Type> { typeof(Tuple<int, int, int>) }; }
    }

    public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
    {
        int item1 = (int)dictionary["Item1"];
        int item2 = (int)dictionary["Item2"];
        int item3 = (int)dictionary["Item3"];
        return new Tuple<int, int, int>(item1, item2, item3);
    }

    public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
    {
        throw new NotImplementedException();
    }
}

To use the converter, you must register it with the serializer like this:

var serializer = new JavaScriptSerializer();
serializer.RegisterConverters(new List<JavaScriptConverter> { new ThreeTupleConverter() });

Then deserialize as you normally would, and it should work fine:

string configJson = @"
{
    ""MyThreeTuple"":
    [
        { ""Item1"": -100, ""Item2"": 20, ""Item3"": 501 },
        { ""Item1"": 100, ""Item2"": 20, ""Item3"": 864 },
        { ""Item1"": 500, ""Item2"": 20, ""Item3"": 1286 }
    ]
}";

var config = serializer.Deserialize<Configuration>(configJson);

foreach (var tuple in config.MyThreeTuple)
{
    Console.WriteLine("(" + tuple.Item1 + ", " + tuple.Item2 + ", " + tuple.Item3 + ")");
}

Output:

(-100, 20, 501)
(100, 20, 864)
(500, 20, 1286)