C# Deserialize JSON with Key Name Starting with String

Question

I have some JSON that looks like this:

{
    "fs_Unique_Form_Name": {
        "title": "Title Text",
        "description": "This is the description.",
        "code": "123"
    },
    "stackId": 1,
    "stateId": 1,
    "timeStamp": "2020-11-04:10.30.48"
}

I am using Newtonsoft.Json to try and deserialize it to a model object, but am having a hard time with the dynamic keys; I'd like to make that property generic if possible since the inner object is always the same.

Here are the models I am trying to use:

public class FormDetail {
    [JsonProperty(PropertyName = "title")]
    public string Title { get; set; }

    [JsonProperty(PropertyName = "description")]
    public string Description { get; set; }

    [JsonProperty(PropertyName = "code")]
    public string Code { get; set; }
}

public class FormResponse {
    [JsonProperty(PropertyName = "NEED TO FIGURE THIS OUT")]
    public FormDetail FormDetail { get; set; }

    [JsonProperty(PropertyName = "stackId")]
    public int StackId { get; set; }

    [JsonProperty(PropertyName = "stateId")]
    public int StateId { get; set; }

    [JsonProperty(PropertyName = "timeStamp")]
    public string TimeStamp { get; set; }
}

I would like to get the whole JSON deserialized into the FormResponse object, but am having difficulty because the fs_Unique_Form_Name key is dynamic after the fs_ portion, but the keys (title, description, code) in that object are static.

Is there a way for me to do something where I can deserialize it to the FormDetail property when the JSON key starts with fs_?

Brian Rogers · Accepted Answer · 2020-11-16 23:01:09Z

You can do this by making a custom JsonConverter for your FormResponse class. Below is the code you would need for the converter:

public class FormResponseConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(FormResponse);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        // Load the JSON into a JObject so we can inspect it.
        JObject obj = JObject.Load(reader);

        // Populate all the known properties on a new instance of FormResponse.
        FormResponse response = new FormResponse();
        serializer.Populate(obj.CreateReader(), response);

        // Now find the first property in the JObject whose name starts with "fs_".
        // If there is one, use it to populate the FormDetail on the response.
        JProperty prop = obj.Properties().FirstOrDefault(p => p.Name.StartsWith("fs_"));
        response.FormDetail = prop != null ? prop.Value.ToObject<FormDetail>(serializer) : null;

        return response;
    }

    public override bool CanWrite
    {
        get { return false; }
    }

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

To use the converter, add a [JsonConverter] attribute to your FormResponse class as shown below. You can remove the [JsonProperty] attribute from the FormDetail property as it is not needed.

[JsonConverter(typeof(FormResponseConverter))]
public class FormResponse
{
    public FormDetail FormDetail { get; set; }

    [JsonProperty(PropertyName = "stackId")]
    public int StackId { get; set; }

    [JsonProperty(PropertyName = "stateId")]
    public int StateId { get; set; }

    [JsonProperty(PropertyName = "timeStamp")]
    public string TimeStamp { get; set; }
}

Then you can deserialize as you normally would:

var response = JsonConvert.DeserializeObject<FormResponse>(json);

Here is a working demo: https://dotnetfiddle.net/jHyRcK

Alexander Petrov · Accepted Answer · 2020-11-16 21:11:35Z

There are many ways to do it.

For example, let's create a custom reader.

class CustomJsonReader : JsonTextReader
{
    public CustomJsonReader(TextReader reader) : base(reader) { }

    public override object Value
    {
        get
        {
            if (base.TokenType == JsonToken.PropertyName &&
                base.Value.ToString().StartsWith("fs_"))
                return "FormDetail";

            return base.Value;
        }
    }
}

Use it like this

FormResponse response;
var serializer = JsonSerializer.CreateDefault();

using (var streamReader = new StreamReader("test.json"))
using (var jsonReader = new CustomJsonReader(streamReader))
{
    response = serializer.Deserialize<FormResponse>(jsonReader);
}

In this case, the FormDetail property does not need the JsonProperty attribute.

Collectives™ on Stack Overflow

C# Deserialize JSON with Key Name Starting with String

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related