Deserialize Json string to C# model

Question

I have the following JSON object which i get to my Web API controller:

{
    "id": "13",
    "title": "party",
    "periods": {
        "0": {
            "label": "Period",
            "start_date": "2015-04-20",
            "end_date": "2015-04-29"
        }
    }
}

I want to try to Deserialize this straight into a Model that i have in C# but I'm not able too.

Here is my Model:

    public class PeriodsModel
    {
        [JsonProperty("id")]
        public int id { get; set; }

        [JsonProperty("title")]
        public string title { get; set; }

        [JsonProperty("periods")]
        public Periods periods { get; set; }
    }
    public class Periods
    {
        [JsonProperty("0")]
        public Dictionary<string,Period> period { get; set; }
    }

    public class Period
    {
        [JsonProperty("label")]
        public string label { get; set; }

        [JsonProperty("start_date")]
        public string start_date { get; set; }

        [JsonProperty("end_date")]
        public string end_date { get; set; }
    }

and here is my method in my controller:

public void Put([FromBody]JToken jsonbody)
{
    var myJsonObject = JsonConvert.SerializeObject(jsonbody);
    PeriodsModel model = JsonConvert.DeserializeObject<PeriodsModel>(myJsonObject);
}

Here is my error msg that i get:

An exception of type 'Newtonsoft.Json.JsonSerializationException' occurred in Newtonsoft.Json.dll but was not handled in user code

Additional information: Error converting value "Period" to type 'CMS.WebApi.Controllers.ActivitiesController+Period'. Path 'periods.0.label', line 1, position 62.

CodingWithSpike · Accepted Answer · 2015-10-01 12:52:57Z

3

the error message is correct. Drill down into the data a little... You have:

    "0": {
        "label": "Period",
        "start_date": "2015-04-20",
        "end_date": "2015-04-29"
    }

And you try to put it into:

public class Periods
{
    [JsonProperty("0")]
    public Dictionary<string,Period> period { get; set; }
}

public class Period
{
    [JsonProperty("label")]
    public string label { get; set; }

    [JsonProperty("start_date")]
    public string start_date { get; set; }

    [JsonProperty("end_date")]
    public string end_date { get; set; }
}

So more specifically, this JSON:

    {
        "label": "Period",
        "start_date": "2015-04-20",
        "end_date": "2015-04-29"
    }

Is being deserialized to a Dictionary<string,Period>

So then the first property:

        "label": "Period"

Needs to be deserialized to a <string, Period> pair. The left side "label" is properly converted to a string but the right side is a string "Period", and that string can not be deserialized into the class type Period

Hence the error

Error converting value "Period" to type 'CMS.WebApi.Controllers.ActivitiesController+Period'

It is trying to convert the string "Period" to the class Period.

It isn't totally clear what you want to do here, but if there is only ever a "0" in periods then you could just change the property to:

public class Periods
{
    [JsonProperty("0")]
    public Period period { get; set; }
}

But my guess is that you would want to have more than 1 period, so you would have "0", "1", "2" ... etc.

Without putting together some code to test it, I'm not sure if there is a good way to do that.

You might want to try making the PeriodsModel have:

    [JsonProperty("periods")]
    public Dictionary<string, Period> periods { get; set; }

and then you wouldn't need a Periods class at all.

Though usually when I have a variable number of things to pass, I just use a JSON array instead, like:

{
    "id": "13",
    "title": "party",
    "periods": [
        {
            "label": "Period1",
            "start_date": "2015-04-20",
            "end_date": "2015-04-29"
        }, {
            "label": "Period2",
            "start_date": "2015-04-20",
            "end_date": "2015-04-29"
        }, {
            "label": "Period3",
            "start_date": "2015-04-20",
            "end_date": "2015-04-29"
        }
    ]
}

answered Oct 1, 2015 at 12:52

CodingWithSpike

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5 Comments

grimsan55 Over a year ago

Yes, I would also like to have an array of objects instead. But I have nothing to do how the Json is formated in the frontend, im only suppose to handle it on server side hence my problem.

CodingWithSpike Over a year ago

@grimsan55 In that case I would try changing the PeriodsModel to have the property: Dictionary<string, Period> periods { get; set; } instead, and see if that works.

grimsan55 Over a year ago

Yes that works, but how do I access lets say the end_date in an easy way ?

CodingWithSpike Over a year ago

@grimsan55 I think this would work: model.periods["0"].start_date because model.periods is a Dictionary with the keys "0", "1", "2", etc... so you would just access the dictionary as usual.

grimsan55 Over a year ago

Thanks, dunno why I couldn't figure it out.. I'll mark your answer as the correct one since you gave such a detailed explanation even tho Asad gave the correct answer as well.

Brian Rogers · Accepted Answer · 2015-10-01 14:02:40Z

1

This is how you could do it, since the "0" is more of a key and not a property variable:

public class PeriodsModel
{
    [JsonProperty("id")]
    public int id { get; set; }

    [JsonProperty("title")]
    public string title { get; set; }

    [JsonProperty("periods")]
    public Dictionary<string, Period> periods { get; set; }
}

public class Period
{
    [JsonProperty("label")]
    public string label { get; set; }

    [JsonProperty("start_date")]
    public string start_date { get; set; }

    [JsonProperty("end_date")]
    public string end_date { get; set; }
}

edited Oct 1, 2015 at 14:02

Brian Rogers

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answered Oct 1, 2015 at 12:43

Asad Palekar

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