JSON deserialization in C# sub array

Question

I'm trying to desearialize the following using Newtonsoft.Json

{
    "max_id_str":"1234567",
    "results":[{
        "created_at":"Tue, 21 May 2013 03:06:23 +0000",
        "from_user":"Name Here",
        "from_user_id":33333,
        "text":"THE TEXT GOES HERE"
    }],
    "results_per_page":1,
    "since_id":0,
    "since_id_str":"0"
}

I can retrieve the max_id_str using desearialization but cannot get any of the data in "results"

Here's the code I have

public class tweet
    {
        public string max_id_str { get; set; }
        public string text{ get; set; }
        public string results_per_page{ get; set; }
        public string since_id { get; set; }
        public string since_id_str { get; set; }
    }

I then create an object of the class and attempt to desearlize it into the object

tweet t = new tweet();
t = JsonConvert.DeserializeObject<tweet>(e.Result);

Everything but "text" populates? Text's value is null when I output the value. Any ideas how to accomplish what I'm trying?

where is corresponding tweet class member? where do you want you results array to be deserialized to? — Konstantin Chernov
– Konstantin Chernov, Commented May 21, 2013 at 3:57

Jeff Mercado · Accepted Answer · 2013-05-21 04:39:23Z

4

I'm not sure what you're expecting to get deserializing that JSON string to that type, text is not a property of the object so there's no reason to expect it to do so like that. text is a property of the objects within the results list. You need to map those objects as well and then access the text through the result objects.

public class tweet
{
    public string max_id_str { get; set; }
    //public string text{ get; set; }
    public List<result> results { get; set; }
    public string results_per_page{ get; set; }
    public string since_id { get; set; }
    public string since_id_str { get; set; }
}

public class result
{
    public string created_at { get; set; }
    public string from_user { get; set; }
    public int from_user_id { get; set; }
    public string text { get; set; }
}

If you were trying to use the values within results to determine the value of your text property, you could write a converter to extract the text value. Just add a JsonProperty and JsonConverter attribute to your text property and implement the converter.

public class tweet
{
    public string max_id_str { get; set; }
    [JsonProperty("results")]
    [JsonConverter(typeof(TextPropertyResultExtractorConverter))]
    public string text { get; set; }
    public string results_per_page{ get; set; }
    public string since_id { get; set; }
    public string since_id_str { get; set; }
}

public class TextPropertyResultExtractorConverter : JsonConverter
{
    public override bool CanConvert(Type type)
    {
        throw new NotImplementedException();
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var results = (JArray)serializer.Deserialize(reader);
        var result = results.First();
        return result.Value<string>("text");
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }
}

edited May 21, 2013 at 4:39

answered May 21, 2013 at 4:08

Jeff Mercado

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4 Comments

Dimitar Dimitrov Over a year ago

I was just gonna write pretty much the same :) Good stuff.

Bawlsout Over a year ago

This answered it for me, thank you. I don't know what exactly I was thinking.

Jeff Mercado Over a year ago

@Bawlsout: Just for kicks, I added an example of a converter that could read that value if that's what you were expecting.

ashes999 Over a year ago

FYI, you can also deserialize to a list of Dynamic and inspect the object that comes back -- what properties it has.

Dimitar Dimitrov · Accepted Answer · 2013-05-21 04:12:47Z

1

It's because text is a child element, whereas in your C# object you're having it directly in tweet. You're missing the results object as a property. There is no way for the deserializer to know where to place those values (there are no corresponding properties).

edited May 21, 2013 at 4:12

answered May 21, 2013 at 4:04

Dimitar Dimitrov

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2 Comments

Bawlsout Over a year ago

Thanks, yours along with Jeff's replies solved my issue. Back at it!

Dimitar Dimitrov Over a year ago

@Bawlsout you got it ;) Cheers

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