C# JSON Deserializing a List of objects within an Object

Question

{
"deviceStatus": {
    "totalDevices": 3,
    "startIndex": 0,
    "utcTimestamp": 1502782784,
    "list": [
        {
            "identifier": "000D6F000A9E6E3D:0",
            "rxTime": 0
        },
        {
            "identifier": "000D6F000BE977F0:0",
            "rxTime": 1502782323,
            "lowBattery": "false",
            "level": "0",
            "batteryLevel": "84"
        },
        {
            "identifier": "000D6F000BE95E24:0",
            "rxTime": 1502782754,
            "lowBattery": "false",
            "level": "0",
            "batteryLevel": "86"
        }
        ]
    }
}




public class Qube
{
    private const string _JSON = "{\"deviceStatus\":{\"totalDevices\":3,\"startIndex\":0,\"utcTimestamp\":1502782784,\"list\":[{\"identifier\":\"000D6F000A9E6E3D:0\",\"rxTime\":0},{\"identifier\":\"000D6F000BE977F0:0\",\"rxTime\":1502782323,\"lowBattery\":\"false\",\"level\":\"0\",\"batteryLevel\":\"84\"},{\"identifier\":\"000D6F000BE95E24:0\",\"rxTime\":1502782754,\"lowBattery\":\"false\",\"level\":\"0\",\"batteryLevel\":\"86\"}]}}";

    public void GetStatus()
    {
        var jsonRootObj = JsonConvert.DeserializeObject<RootObject>(_JSON);

        Console.WriteLine(string.Format("Total Devices = {0}, Start Index = {1}, Timestamp = {2}",jsonRootObj.deviceStatus.totalDevices,jsonRootObj.deviceStatus.startIndex,jsonRootObj.deviceStatus.utcTimestamp));

        Console.WriteLine(string.Format("Device 1 ID = {0}",jsonRootObj.deviceStatus.device[0].identifier));

        Console.ReadLine();
    }

}

public class Device
{
    public string identifier { get; set; }
    public int rxTime { get; set; }
    public string lowBattery { get; set; }
    public string level { get; set; }
    public string batteryLevel { get; set; }
}

public class DeviceStatus
{
    public int totalDevices { get; set; }
    public int startIndex { get; set; }
    public int utcTimestamp { get; set; }
    public List<Device> device { get; set; }
}

public class RootObject
{
    public DeviceStatus deviceStatus { get; set; }
}

Im trying to Deserialize the JSON string that I receive from a ethernet device. The JSON string that I receive is above.

I have worked out how to deserialize to get to the DeviceStatus.totalDevices, .startIndex, .utcTimestamp etc.

But when i do the Console.WriteLine(string.Format("Device 1 ID = {0}",jsonRootObj.deviceStatus.device[0].identifier)); I get an exception

Object reference not set to an instance of an object

Im sure that im missing something very simple but this is my first ever C# project so cant work it out.

I've done quite alot of searching on here to get me to this point but just cant get any further.

Thanks

Possible duplicate of What is a NullReferenceException, and how do I fix it? — Matthias Burger
– Matthias Burger, Commented Aug 15, 2017 at 10:09
in your json, the property list must be named device or rename the property device using [JsonProperty("list")] - and your json is invalid. you're missing a } at the end — Matthias Burger
– Matthias Burger, Commented Aug 15, 2017 at 10:12

Matthias Burger · Accepted Answer · 2017-08-15 10:17:53Z

4

in your json, the property list must be named device or rename the property device using [JsonProperty("list")]:

public class DeviceStatus
{
    public int totalDevices { get; set; }
    public int startIndex { get; set; }
    public int utcTimestamp { get; set; }

    [JsonProperty("list")]
    public List<Device> device { get; set; }
}

otherwise Json.Net doesn't know which property list belongs to and the value is null - here you get the NullReferenceException you mentioned

answered Aug 15, 2017 at 10:17

Matthias Burger

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Comments

Erik Bongers · Accepted Answer · 2017-08-15 10:19:11Z

0

As Matthias Burger said, the name of your "list" doesn't match, hence your device member will be empty (or even null, in this case, I think).

answered Aug 15, 2017 at 10:19

Erik Bongers

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