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Vandel212
Vandel212

Reputation: 1144

How to deserialize json into C# List Object

I seem to be running into an issue where I try to deserialize a json array into a C# list (I'm using Json.NET). The problem is I'm getting an error:

Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'ProjectName.WebServices.EventWebMethods+ServiceItem' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly. To fix this error either change the JSON to a JSON object (e.g. {"name":"value"}) or change the deserialized type to an array or a type that implements a collection interface (e.g. ICollection, IList) like List that can be deserialized from a JSON array. JsonArrayAttribute can also be added to the type to force it to deserialize from a JSON array. Path '[0]', line 1, position 2.

This is my json code which is created by taking a javascript array and using JSON.stringify on it:

[["6249","Locked"],["6250","Locked"],["6251","Locked"]]

This is the C# code I am using:

    [Serializable]
    public class ServiceItem
    {
        long lngId{ get; set; }
        string strStatus{ get; set; }

        public ServiceItem() { }
    }

    [WebMethod(EnableSession = true)]
    public string Create(string strJSON)
    {
        //Error happens on this next line:
        List<ServiceItem> ServiceData = JsonConvert.DeserializeObject<List<ServiceItem>>(strJSON);
        return "test";
    }

How do I get this to deserialize into the C# class. Any help is appreciated!

UPDATE

I made the changes to my javascript so that it includes the variable names as per suggested. Still same error. Here is the JSON in the C# variable:

[
[\"lngId\" : \"6249\",\"strStatus\" : \"Locked\"],
[\"lngId\" : \"6250\",\"strStatus\" : \"Locked\"],
[\"lngId\" : \"6251\",\"strStatus\" : \"Locked\"]
]

Are the curly braces that important, and if that is the problem, why doesn't JSON.Stringify do that?

UPDATE 2

Figured it out. I needed to create each json item like this:

arrServices.push({"lngId": intServiceID, "strStatus" : "Locked"});

Now it works. Thank you for the help!

Upvotes: 1

Views: 846

Answers (1)

Jason Boyd
Jason Boyd

Reputation: 7029

Your example JSON represents an array of arrays of strings. The JSON that represents the schema represented by your ServiceItem class would look like this:

[  
   {  
      "lngID":"6249",
      "strStatus":"Locked"
   },
   {  
      "lngID":"6250",
      "strStatus":"Locked"
   },
   {  
      "lngID":"6251",
      "strStatus":"Locked"
   }
]

You need to serialize your data on the other end differently (so that it matches your class). If that is not an option then you are going to have to manually deserialize the JSON on the server:

List<ServiceItem> ServiceData =
    JArray
    .Parse(input)
    .Select(x => x.ToArray())
    .Select(x => new ServiceItem()
        {
            lngId = x[0].Value<int>(),
            strStatus = x[1].Value<String>()
        })
    .ToList();

Or implement a custom JsonConverter.

Upvotes: 4

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