json newtonsoft : Deserialize Object containing a list of string

I have the following issue with this json :

{
"EVTS": {
"EVT": [
  { "ID": "123456",
    "KEY1" : "somekey",
    "CATEG": [
      "cat1",
      "cat2",
      "cat3"
    ]
  }
  ]}
  }

and this c# class:

public class myClass{
    public string ID { get; set; }
    public string KEY1 { get; set; } 

    public list<string> CATEG { get; set; } 
}

public class ESObject1
{

    [JsonProperty("EVT")]
    public List<myClass> EVT { get; set; }
}

public class ESObject0
{

    [JsonProperty("EVTS")]
    public ESObject1 EVTS { get; set; }
}

}

here i call the deserializer :

ESObject0 globalobject = JsonConvert.DeserializeObject<ESObject0>(json);

But this last code doesnt work, i throws this exception : System.ArgumentException: Could not cast or convert from System.String to System.Collections.Generic.List1[System.String].`

Instead of list<string> i used string [] and only string nothing seems to work.

how can i deserialize this object correctly please.

Thank you.

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

There doesn’t seem to be any apparent problem wit hyour code as this working example illustrates:

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

public class myClass
{
    public string ID { get; set; }
    public string KEY1 { get; set; } 
    public List<string> CATEG { get; set; } 
}

public class ESObject1
{
    [JsonProperty("EVT")]
    public List<myClass> EVT { get; set; }
}

public class ESObject0
{
    [JsonProperty("EVTS")]
    public ESObject1 EVTS { get; set; }
}


class Program
{
    static void Main()
    {
        string json = 
        @"{
            ""EVTS"": {
                ""EVT"": [
                    {
                        ""ID"": ""123456"",
                        ""KEY1"": ""somekey"",
                        ""CATEG"": [
                            ""cat1"",
                            ""cat2"",
                            ""cat3""
                        ]
                    }
                ]
            }
        }";

        ESObject0 globalobject = JsonConvert.DeserializeObject<ESObject0>(json);
        foreach (string item in globalobject.EVTS.EVT[0].CATEG)
        {
            Console.WriteLine(item);
        }
    }
}

Maybe you just fed a wrong json value to the deserializer which doesn’t look like as the one shown in your question. By the way, the one shown i nyour question is invalid JSON as you are missing a , after KEY1 property declaration.

UPDATE:

Now that you have shown your real JSON (coming from http://donnees.ville.quebec.qc.ca/Handler.ashx?id=69&f=JSON) it appears that there’s a row where CATEG is not an array of strings but a simple string:

""CATEG"": ""Conférence""

Now that’s a pretty bad design because they are mixing arrays and simple properties. I am afraid that in order to deal with this situation you will need to use JObjects and extract the information you need by testing the actual underlying type.

For example:

var obj = JObject.Parse(json);
var events = (JArray)obj["EVTS"]["EVT"];
foreach (JObject evt in events)
{
    var categories = evt["CATEG"];
    if (categories is JArray)
    {
        // you've got a list of strings so you can loop through them
        string[] cats = ((JArray)categories)
            .Select(x => x.Value<string>())
            .ToArray();
    }
    else
    {
        // you've got a simple string
        string cat = categories.Value<string>();
    }
}

Method 2

I have done this many times with many many headaches. My advice is take the json output and use a tool similar to this to write your class for you (http://json2csharp.com/).

Then go over any nullable variables and add nullable type (ex. using int? for int) where needed.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0