CODEWITHSUNDEEP
c#jsonxamarinjson.net
G Gr
G Gr

Reputation: 6080

Invalidcastexception JsonConvert.DeserializeObject

I am getting an invalid cast exception that the specified cast is not valid. On this line:

RootObject mountain = JsonConvert.DeserializeObject<RootObject>(json1);

From the documentation this should be fine? I can see the console output is fine?

Response: [{"Height_ft": 2999.0, "Height_m": 914.0, "ID": "c1", "Latitude": 57.588007, "Longitude": -5.5233564, "Name": "Beinn Dearg", "humidity": 0.81, "snowCover": 4.99, "temperature": 63.0}]

        Spinner spinner = (Spinner)sender;
        string urlmountain = "http://removed.azurewebsites.net/api/Mountains?name=";
        JsonValue json1 = FetchMountain(urlmountain+string.Format("{0}", spinner.GetItemAtPosition(e.Position)));
        //below.................................
        RootObject mountain = JsonConvert.DeserializeObject<RootObject>(json1); //this line
        string toast = mountain.Name;
        Toast.MakeText(this, toast, ToastLength.Long).Show();

    private JsonValue FetchMountain(string urlmountain)
    {
        // Create an HTTP web request using the URL:
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(urlmountain));
        request.ContentType = "application/json";
        request.Method = "GET";

        // Send the request to the server and wait for the response:
        using (WebResponse response = request.GetResponse())
        {
            // Get a stream representation of the HTTP web response:
            using (Stream stream = response.GetResponseStream())
            {
                // Use this stream to build a JSON document object:
                JsonValue jsonDoc1 = JsonObject.Load(stream);
                Console.Out.WriteLine("Response: {0}", jsonDoc1.ToString());

                // Return the JSON document:
                return jsonDoc1;
            }
        }
    }
    public class RootObject
    {
        public string ID { get; set; }

        public double? Latitude { get; set; }

        public double? Longitude { get; set; }

        public string Name { get; set; }

        public double? Height_m { get; set; }

        public double? Height_ft { get; set; }

        public double? temperature { get; set; }

        public double? humidity { get; set; }

        public double? snowCover { get; set; }

        public override string ToString()
        {
            return Name;
        }
    }

Upvotes: 3

Views: 2876

Answers (2)

dana
dana

Reputation: 18145

It looks like your JSON is an Array of objects. You should be able to deserialize the array and get the first one like so:

RootObject mountain = JsonConvert.DeserializeObject<RootObject[]>(json1)[0];

One thing to note is that you are sort of mixing technologies here. JsonValue is from the System.Json namespace, whereas JsonConvert is from the Newtonsoft.Json (i.e. JSON.Net) namespace. If you wanted to go strictly with JSON.Net, you could do something like this:

private RootObject FetchMountain(string urlmountain)
{
    // Create an HTTP web request using the URL:
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(urlmountain));
    request.ContentType = "application/json";
    request.Method = "GET";

    using (WebResponse response = request.GetResponse())
    using (Stream stream = response.GetResponseStream())
    using (StreamReader streamReader = new StreamReader(stream))
    {
        JsonSerializer serializer = new JsonSerializer();
        RootObject[] mountains = (RootObject[])serializer.Deserialize(streamReader, typeof(RootObject[]));
        return (mountains.Length > 0) ? mountains[0] : null;
    }
}

Upvotes: 3

David L
David L

Reputation: 33833

The json data being returned is an array of objects, not a single object, as denoted by the opening and closing brackets []. You need to deserialize to an array or a list:

var mountains = JsonConvert.DeserializeObject<List<RootObject>>(json);

To access the first mountain from the deserialized payload, use .FirstOrDefault().

var mountain = mountains.FirstOrDefault();
if (mountain != null)
{
    string toast = mountain.Name;
    Toast.MakeText(this, toast, ToastLength.Long).Show();
}

Upvotes: 5

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