Deserialize list of JSON objects

Question

I got a Windows Phone 8.1 app.

I am trying to parse a list of objects returned by my Web API call.

On my server I have this code:

Default.aspx:

[WebMethod]
public static List<Shared.PremisesResponse> GetPremises(string emailaddress)
{
    Premises premises = new Premises();
    return premises.GetPremises(emailaddress);
}

In that premise object class

    public List<Shared.PremisesResponse> GetPremises(string emailAlias)
    {
        DAL dal = new DAL();
        List<Shared.PremisesResponse> premises = new List<Shared.PremisesResponse>();

        try
        {
            DataSet dtMacs = dal.GetMacs(emailAlias);

            for (int index = 0; index < dtMacs.Tables[0].Rows.Count; index++)
            {
                Shared.PremisesResponse itemMAC1 = new Shared.PremisesResponse();
                itemMAC1.PremiseName = dtMacs.Tables[0].Rows[index]["PremiseName"].ToString().Trim();
                itemMAC1.Alias = dtMacs.Tables[0].Rows[index]["Alias"].ToString().Trim();
                premises.Add(itemMAC1);
            }
        }
        catch (Exception ex)
        {
            Email2.SendError("Premises.GetPremises:" + ex.ToString(), emailAlias);
            Shared.PremisesResponse itemMAC1 = new Shared.PremisesResponse();
            itemMAC1.PremiseName = "ERROR";
            itemMAC1.Alias = ex.ToString();
            premises.Add(itemMAC1);
        }
        return premises;
    }

The class Shared.Premise:

    public class PremisesResponse
    {
        public string PremiseName;
        public string Alias;
    }

In my WP8.1 client app:

    public async static Task<List<D2>> GetPremises( string emailaddress)
    {
        List<D2> premises = new List<D2>();
        try
        {
            using (var client = new HttpClient())
            {
                var resp = await client.PostAsJsonAsync("http://my url/NativeApp/Default.aspx/GetPremises",
                                                         new { emailaddress = emailaddress });

                var str = await resp.Content.ReadAsStringAsync();
                var premisesResponse = JsonConvert.DeserializeObject<List<D2>>(str);
                foreach (var pr in premisesResponse)
                {
                    D2 d2 = new D2();
                    d2.Alias = pr.Alias;
                    d2.PremiseName = pr.PremiseName;
                    premises.Add(d2);
                }
            }
        }
        catch (Exception ex)
        {
            //evMessage(Enums.MessageType.Error, serverRegister);
        }
        return premises;
    }

And the objects I am using in my client:

public class D2
{
    public string __type { get; set; }
    public string PremiseName;
    public string Alias;
}
public class PremisesResponse
{
    public D2 d { get; set; }
}

'var str' returns this value:

{"d":[{"__type":"InformedMotionBiz.Shared+PremisesResponse","PremiseName":"Informatica 2000","Alias":"9A5C3-E1945-3D315-BB43C"},{"__type":"InformedMotionBiz.Shared+PremisesResponse","PremiseName":"My Office","Alias":"40387-69918-FC22F-C444B"}]}

The error occurs on this line:

var premisesResponse = JsonConvert.DeserializeObject<List<PremisesResponse>>(str);

The error message is:

[Informed.D2]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly. To fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array or List) that can be deserialized from a JSON object. JsonObjectAttribute can also be added to the type to force it to deserialize from a JSON object.
Path 'd', line 1, position 5.

I have no problems returning a single value, just with returning a list of this object.

Any pointers would be helpful.

Thanks

Answer 1

You're trying to deserialize a List<D2> rather than a single D2 object:

public class PremisesResponse
{
    public D2[] d { get; set; }
}

And then simply:

PremisesResponse response = JsonConvert.DeserializeObject<PremisesResponse>(str);