How to deserialize a json without knowing the format?

Question

I use RestSharp and I have a problem when I deserialize a Json.

In case of success, I receive a Json like that (data is a table):

{"status": "OK", "data": "[...]"}

and in case of error, I receive a Json like (data is a string):

{"status": "ERROR", "data": "..."}

How can I know if I have to deserialize the Json with a table or with a string?

My method is something like that (it returns a table but crashes if the Json returns a string as data) :

public Task<Items> GetItemById(string id)
{
var client =
new RestClient(string.Format("{0}/{1}/{2}/{3}/{4}", _baseUrl, 
    AppResources.RestApiVersion, userId, token, AppResources.NotUse));

var tcs = new TaskCompletionSource<Items>();
var request = new RestRequest(string.Format("/items/get/{0}", id));
client.ExecuteAsync<Items>(request, response => {
    try
    {
        tcs.SetResult(new JsonDeserializer().Deserialize<Items>(response));
    }
    catch (InvalidCastException e)
    {

    }
});
return tcs.Task;
}

score 0 · Answer 1 · edited May 23 '17 at 12:15

I use code from this answer: Deserialize JSON into C# dynamic object?

It generates a dynamic object depending on the content of the JSON object. I like it quite a bit, though his code has several bugs that I have fixed in my version below:

internal sealed class DynamicJsonConverter : JavaScriptConverter
{
    public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
    {
        if (dictionary == null)
            throw new ArgumentNullException("dictionary");

        return type == typeof(object) ? new DynamicJsonObject(dictionary) : null;
    }

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

    public override IEnumerable<Type> SupportedTypes
    {
        get { return new ReadOnlyCollection<Type>(new List<Type>(new[] { typeof(object) })); }
    }

    #region Nested type: DynamicJsonObject

    private sealed class DynamicJsonObject : DynamicObject
    {
        private readonly IDictionary<string, object> _dictionary;

        public DynamicJsonObject(IDictionary<string, object> dictionary)
        {
            if (dictionary == null)
                throw new ArgumentNullException("dictionary");
            _dictionary = dictionary;
        }

        public override string ToString()
        {
            var sb = new StringBuilder();
            ToString(sb);
            return sb.ToString();
        }

        private void ToString(StringBuilder sb)
        {
            sb.Append("{");
            var firstInDictionary = true;
            foreach (var pair in _dictionary)
            {
                if (!firstInDictionary)
                    sb.Append(",");
                firstInDictionary = false;
                var value = pair.Value;
                var name = pair.Key;
                if (value is string)
                {
                    sb.AppendFormat("\"{0}\":\"{1}\"", name, value);
                }
                else if (value is IDictionary<string, object>)
                {
                    sb.AppendFormat("\"{0}\":", name);
                    new DynamicJsonObject((IDictionary<string, object>)value).ToString(sb);
                }
                else if (value is ArrayList)
                {
                    sb.Append("\"");
                    sb.Append(name);
                    sb.Append("\":[");
                    var firstInArray = true;
                    foreach (var arrayValue in (ArrayList)value)
                    {
                        if (!firstInArray)
                            sb.Append(",");
                        firstInArray = false;
                        if (arrayValue is IDictionary<string, object>)
                            new DynamicJsonObject((IDictionary<string, object>)arrayValue).ToString(sb);
                        else if (arrayValue is string)
                            sb.AppendFormat("\"{0}\"", arrayValue);
                        else
                            sb.AppendFormat("{0}", arrayValue);

                    }
                    sb.Append("]");
                }
                else
                {
                    sb.AppendFormat("\"{0}\":{1}", name, value);
                }
            }
            sb.Append("}");
        }

        public override bool TryGetMember(GetMemberBinder binder, out object result)
        {
            if (!_dictionary.TryGetValue(binder.Name, out result))
            {
                // return null to avoid exception.  caller can check for null this way...
                result = null;
                return true;
            }

            var dictionary = result as IDictionary<string, object>;
            if (dictionary != null)
            {
                result = new DynamicJsonObject(dictionary);
                return true;
            }

            var arrayList = result as ArrayList;
            if (arrayList != null && arrayList.Count > 0)
            {
                if (arrayList[0] is IDictionary<string, object>)
                    result = new List<object>(arrayList.Cast<IDictionary<string, object>>().Select(x => new DynamicJsonObject(x)));
                else
                    result = new List<object>(arrayList.Cast<object>());
            }

            return true;
        }
    }

    #endregion
}

The rest of his code example is applicable.

Well, you don't really want to just deserialize the list, though. To deserialize the list, you have to deserialize the content of the list, which will be objects with non-list properties. I mean, if in the main object you only wanted the list objects, you could create a static "depth" variable that you increment in `ToString()` (it's recursive) and increment depth at the beginning of `ToString()` and decrement it at the end and only handle the first and second `if` statements when depth > 0. The third if (`else if (value is ArrayList)`) handles the list. — Pete, Nov 01 '13 at 18:13

How to deserialize a json without knowing the format?

1 Answers1