Deserialize JSON single string to array

Question

I am trying to deserialize my json data however my class is not set up properly I do not have access to change the json response, so I need to write a function to handle the json properly.

Here is the data

{
  "blabla": {
    "-Score": "1",
    "-Ref": "50",
    "foo": {
      "-colour": "Yellow",
      "-ref": "y50"
    }
  }
}

however some times the data will be

    {
  "blabla": {
    "-Score": "1",
    "-Ref": "50",
    "foo": [
      {
        "-colour": "Yellow",
        "-ref": "y50"
      },
      {
        "-colour": "Green",
        "-ref": "g50"
      },
      {
        "-colour": "Red",
        "-ref": "r50"
      }
    ]
  }
}

This class works for the first data

public class blabla
{
    public Foo Foo {get; set;}
}

And this class works for the second data

public class blabla
{
    public Foo[] Foo {get; set;}
}

But how can I get the class to work for both?

"For ease of reading" it would be far better if you showed the actual JSON. You're asking us how to deserialize what we imagine the JSON representation of those two examples might be. — Paul Roub
– Paul Roub, Commented Jul 2, 2015 at 14:03
Do you have any control over the JSON format? "Sometimes it's an array, sometimes it's not" is not the sanest representation ever. "Always an array, even if there's just one" will make lives easier on both the serialization and de-serialization sides. — Paul Roub
– Paul Roub, Commented Jul 2, 2015 at 14:10
Not sure if this is of use, but it seems to be a similar problem - michaelcummings.net/mathoms/… — JJJCoder
– JJJCoder, Commented Jul 2, 2015 at 14:22
If you can use JSON.net, then it's easy to write a custom converter. Your blabla class would have a Foo[] property and you'd use the custom converter to examine the foo property and populate the array. — Matt Burland
– Matt Burland, Commented Jul 2, 2015 at 14:49

Arthur Rey · Accepted Answer · 2015-07-24 09:41:28Z

Here are the basic classes:

public class Test
{
    public Blabla blabla { get; set; }
}

public class Blabla
{
    public string _score { get; set; }
    public string _ref { get; set; }

    [JsonConverter(typeof(FooConverter))]
    public Foo[] foo { get; set; }
}

public class Foo
{
    public string _colour { get; set; }
    public string _ref { get; set; }
}

Set type of foo to be Foo[] no matter what the data is, and add [JsonConverter(typeof(FooConverter))] to use a custom converter.

Here is the custom converter:

public class FooConverter : JsonConverter
{
    // Declared as abstract in JsonConverter so must be overridden
    public override bool CanConvert(Type objectType) { return true; }

    // Declared as abstract in JsonConverter so must be overridden
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) { }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        JToken token = JToken.Load(reader);

        return token.Type == JToken.Array ? token.ToObject<Foo[]>() : new Foo[] { token.ToObject<Foo>() };
    }
}

In the ReadJson method we load the data in a token and we check whether the data is an array or a plain object. If it is already an array we just return the array object as Foo[] and if it is a plain object we return a new Foo[] containing our plain object.

Here is a test case:

string json1 = @"{
                  ""blabla"": 
                    {
                      ""_score"": ""1"",
                      ""_ref"": ""50"",
                      ""foo"": 
                        {
                          ""_colour"": ""Yellow"",
                          ""_ref"": ""y50""
                        }
                    }
                }";

string json2 = @"{
                 ""blabla"": 
                    {
                      ""_score"": ""1"",
                      ""_ref"": ""50"",
                      ""foo"": 
                        [
                          {
                            ""_colour"": ""Yellow"",
                            ""_ref"": ""y50""
                          },
                          {
                            ""_colour"": ""Green"",
                            ""_ref"": ""g50""
                          },
                          {
                            ""_colour"": ""Red"",
                            ""_ref"": ""r50""
                          }
                        ]
                    }
                }";

Test test1 = JsonConvert.DeserializeObject<Test>(json1);
Test test2 = JsonConvert.DeserializeObject<Test>(json2);

You will always have an array but there will be 1 element in the first test case, and 3 elements in the second test case.

jamiii · Accepted Answer · 2015-07-02 14:25:46Z

1

go to json2csharp.com
paste your json data
generate the class

there you go :)

using Newtonsoft.Json;
using (WebClient wc = new WebClient())
{
    var json = wc.DownloadString(url);
    var t = JsonConvert.DeserializeObject<whateverClass.you.have.made>(json);
}

edited Jul 2, 2015 at 14:25

answered Jul 2, 2015 at 14:20

jamiii

192 bronze badges

2 Comments

DaGeezah Over a year ago

thanks, but no - if you paste first data, it sets it to a string, and if you paste second one, puts it as an array.

jamiii Over a year ago

what about checking if the variable has elements on it? sth like... if (t.response.foo.Count != 0)

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