How to deserialize a JSON with array of strings using "System.Runtime.Serialization.Json" class in C#?

Question

I am working with C# project in which, most data was of basic type all these days such as string, int, bool. Our client imprlements the JSON with System.Runtime.Serialization.Json, where we deserialize JSON sent from a server that is implemented in C++.

So for instance if I had to De-serialize a JSON sent from the server with 2 string keys such as:

{
    "key1":"value1",
    "key2":"value2"
}

we would define a class such as

[DataContract]
public class DeserializeKeys
{
    [DataMember] public string key1 { get; set; }
    [DataMember] public string key2 { get; set; }
};

Our server side code has changed to now send array of strings as a value as shown in the JSON object below:

{
    "key1":"value1",
    "key2":
        [
            "arrayValue1",
            "arrayValue2",
            "arrayValue3"
        ]
}

Please help me write a corresponding class that can deserialize the given JSON using "System.Runtime.Serialization.Json" class in C#.

I have already tried:

[DataContract]
public class DeserializeKeys
{
    [DataMember] public string key1 { get; set; }
    [DataMember] public string[] key2 { get; set; }
};

and

[DataContract]
public class DeserializeKeys
{
    [DataMember] public string key1 { get; set; }
    [DataMember] public List<string> key2 { get; set; }
};

but I am getting null for key2 upon deserialization.

What is the right way to define a class so that the JSON deserialization of array of string happens just as it works currently for a single string.

Krzysztof Krzeszewski · Accepted Answer · 2019-09-20 08:33:36Z

2

Seems to work correctly for me (both string[] and List<string> ) i'll assume that you deserialized it in a wrong way. Here is a minimal example that should get your started on fixing your app.

using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Json;
using System.Text;

namespace Serializator
{
    public class Serializator
    {
        static public SomeClass ReadToObject(string json)
        {
            MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(json));
            DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(SomeClass));
            var deserialized = ser.ReadObject(ms) as SomeClass;
            ms.Close();
            return deserialized;
        }
    }
    [DataContract]
    public class SomeClass
    {
        [DataMember] public string key1 { get; set; }
        [DataMember] public List<string> key2 { get; set; }
    };
    class Program
    {
        static void Main(string[] args)
        {
            SomeClass sc = Serializator.ReadToObject("{\"key1\":\"value1\", \"key2\":[\"arrayValue1\", \"arrayValue2\", \"arrayValue3\"]}");
            foreach(var item in sc.key2)
            {
                Console.WriteLine(item);
            }
        }
    }
}

As it seems the issue lay in a data format not serialization mechanizm (the values of keys were also serialized objects) here is an updated version for the particular format the application required.

using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Json;
using System.Text;

namespace Serializator
{
    public class Serializator
    {
        static public Object ReadToObject(string json, Type t)
        {
            MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(json));
            DataContractJsonSerializer ser = new DataContractJsonSerializer(t);
            var deserialized = ser.ReadObject(ms);
            ms.Close();
            return deserialized;
        }
    }
    [DataContract]
    public class IntermediateClass
    {
        [DataMember] public string error { get; set; }
        [DataMember] public List<string> group { get; set; }
    };

    [DataContract]
    public class ErrorClass
    {
        [DataMember] public string ErrorCode { get; set; }
        [DataMember] public string ErrorMessage { get; set; }
    };

    public class GroupClass
    {
        [DataMember] public int ID { get; set; }
        [DataMember] public string Name { get; set; }
    }

    public class CombinedClass
    {
        public ErrorClass error { get; set; }
        public List<GroupClass> group { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            CombinedClass cb = new CombinedClass();
            IntermediateClass ic = (IntermediateClass)Serializator.ReadToObject("{\"error\":\"{\\n \\\"ErrorCode\\\" : 0,\\n \\\"ErrorMessage\\\" : \\\"Success.\\\"\\n}\\n\",\"group\":[\"{\\n \\\"ID\\\" : 1,\\n \\\"Name\\\" : \\\"Student1\\\"\\n}\\n\",\"{\\n \\\"ID\\\" : 2,\\n \\\"Name\\\" : \\\"Student2\\\"\\n}\\n\"]}", typeof(IntermediateClass));
            cb.group = new List<GroupClass>();
            foreach (var item in ic.group)
            {
                cb.group.Add((GroupClass)Serializator.ReadToObject(item, typeof(GroupClass)));
            }
            cb.error = (ErrorClass)Serializator.ReadToObject(ic.error, typeof(ErrorClass));
            Console.WriteLine(cb.error.ErrorCode);
            Console.WriteLine(cb.error.ErrorMessage);
            Console.WriteLine(cb.group[0].Name);
            Console.WriteLine(cb.group[0].ID);
            Console.WriteLine(cb.group[1].Name);
            Console.WriteLine(cb.group[1].ID);
        }
    }
}

edited Sep 20, 2019 at 8:33

answered Sep 19, 2019 at 13:53

Krzysztof Krzeszewski

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7 Comments

Ganesh Kamath - 'Code Frenzy' Over a year ago

Hi. Thank you for your solution. It is working on the samle code I have written. My exact string looks like this

"{\"error\":\"{\\n   \\\"ErrorCode\\\" : 0,\\n   \\\"ErrorMessage\\\" : \\\"Success.\\\"\\n}\\n\",\"group\":[\"{\\n   \\\"ID\\\" : 1,\\n   \\\"Name\\\" : \\\"Student1\\\"\\n}\\n\",\"{\\n   \\\"ID\\\" : 2,\\n   \\\"Name\\\" : \\\"Student2\\\"\\n}\\n\"]}"

this string is returning null for some reason. Could you please check.

Krzysztof Krzeszewski Over a year ago

@GaneshKamath-'CodeFrenzy' your format is just very weird, what are all those unnecessary slashes doing in there. If i were to unescape it it would still have slashed in all the wrong places, meaning it's not a valid JSON format. No wonder it doesn't work for you. It looks to me like you have an object of format {error: string} where string is an error object converted to string before serialization

Krzysztof Krzeszewski Over a year ago

updated my answer to match your requirements (parsed your json twice)

Ganesh Kamath - 'Code Frenzy' Over a year ago

Hi, yes it is a very wierd string. I will see if there is a more simple example and post back here. I wll also look for alternative solution to my problem. Thank you for your support.

Krzysztof Krzeszewski Over a year ago

there is no need as i provided you with a solution that works with your string (the second code block)

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