Aditya Sharma Aditya Sharma - 2 months ago 10
C# Question

Error reading JObject from JsonReader. Current JsonReader item is not an object: StartArray. Path

I am working on a windows phone 8.1 application involving location. I am receiving Json data from my API. My API return data looks like:

[
{
"country": "India",
"city": "Mall Road, Gurgaon",
"area": "Haryana",
"PLZ": "122002",
"street": "",
"house_no": "",
"POI": "",
"type": "17",
"phone": "",
"lng": 77.08972334861755,
"lat": 28.47930118040612,
"formatted_address": "Mall Road, Gurgaon 122002, Haryana, India"
},
{
"country": "India",
"city": "Mall Road, Kanpur",
"area": "Uttar Pradesh",
"PLZ": "208004",
"street": "",
"house_no": "",
"POI": "",
"type": "17",
"phone": "",
"lng": 80.35783410072327,
"lat": 26.46026740300029,
"formatted_address": "Mall Road, Kanpur 208004, Uttar Pradesh, India"
},
{
"country": "India",
"city": "Mall Road Area, Amritsar",
"area": "Punjab",
"PLZ": "143001",
"street": "",
"house_no": "",
"POI": "",
"type": "17",
"phone": "",
"lng": 74.87286686897278,
"lat": 31.64115178002094,
"formatted_address": "Mall Road Area, Amritsar 143001, Punjab, India"
},
{
"country": "India",
"city": "Vasant Kunj (Mall Road Kishan Garh), New Delhi",
"area": "Delhi",
"PLZ": "110070",
"street": "",
"house_no": "",
"POI": "",
"type": "18",
"phone": "",
"lng": 77.1434211730957,
"lat": 28.51363217008815,
"formatted_address": "Vasant Kunj (Mall Road Kishan Garh), New Delhi 110070, Delhi, India"
}


]

I am deserializing my Json data and putting it into a class named LocationData.
As I run my code it gives me an exception error :
Error reading JObject from JsonReader. Current JsonReader item is not an object: StartArray. Path

where am I going wrong. below is my code

private async void GetAPIData()
{
string _serviceUrl = "https://api.myweblinkapiprovider/v2&q=" + UserRequestedLocation;
HttpClient client = new HttpClient();

HttpResponseMessage responce = await client.GetAsync(new Uri(_serviceUrl));

if (responce.Content != null)
{
var respArray = JObject.Parse(await responce.Content.ReadAsStringAsync());
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.NullValueHandling = NullValueHandling.Ignore;
settings.MissingMemberHandling = MissingMemberHandling.Ignore;
var rcvdData = JsonConvert.DeserializeObject<LocationData>(respArray.ToString(), settings);
UpdateMapData(rcvdData);
UpdateTextData(rcvdData);
}
}


I also tried to use a Jarray my code is as below:

private async void GetAPIData()
{
string _serviceUrl = "https://api.myweblinkprovider.com/v3?fun=geocode&lic_key=MyKey" + UserRequestedLocation;
HttpClient client = new HttpClient();

HttpResponseMessage responce = await client.GetAsync(new Uri(_serviceUrl));

JArray arr = JArray.Parse(await responce.Content.ReadAsStringAsync());

foreach (JObject obj in arr.Children<JObject>())
{
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.NullValueHandling = NullValueHandling.Ignore;
settings.MissingMemberHandling = MissingMemberHandling.Ignore;
var rcvdData = JsonConvert.DeserializeObject<LocationData>(arr.ToString(), settings);
UpdateMapData(rcvdData);
UpdateTextData(rcvdData);
}
}


it gives me an error : Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'MMI_SpeechRecog.Model.LocationData' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.
I need help!

Answer

The first part of your question is a duplicate of Why do I get a JsonReaderException with this code?, but the most relevant part from that (my) answer is this:

[A] JObject isn't the elementary base type of everything in JSON.net, but JToken is. So even though you could say,

object i = new int[0];

in C#, you can't say,

JObject i = JObject.Parse("[0, 0, 0]");

in JSON.net.

What you want is JArray.Parse, which will accept the array you're passing it (denoted by the opening [ in your API response). This is what the "StartArray" in the error message is telling you.

As for what happened when you used JArray, you're using arr instead of obj:

var rcvdData = JsonConvert.DeserializeObject<LocationData>(arr /* <-- Here */.ToString(), settings);

Swap that, and I believe it should work.

Although I'd be tempted to deserialize arr directly as an IEnumerable<LocationData>, which would save some code and effort of looping through the array. If you aren't going to use the parsed version separately, it's best to avoid it.