C# JSON Parsing Issue

Question

Hi I am currently doing my final year project and nearly at the end. However, I am stuck on one small thing which is parsing the below JSON string in C#.

My Bad... copied and pasted an excerpt from the JSON file. Here is the whole JSON string which is valid when I checked jsonutils.org

{ 
    "activities-steps" : [ 
        { 
            "dateTime" : "2016-02-10",
            "value" : "2624"
        } 
    ],
    "activities-steps-intraday" : { 
        "dataset" : [ 
        { 
            "time" : "00:00:00",
            "value" : 0
        },
        { 
            "time" : "00:01:00",
            "value" : 0
        },
        { 
            "time" : "00:02:00",
            "value" : 0
        },
        { 
            "time" : "00:03:00",
            "value" : 0
        },
        { 
            "time" : "00:04:00",
            "value" : 0
        },
        { 
            "time" : "00:05:00",
            "value" : 0
        },
        { 
            "time" : "00:06:00",
            "value" : 0
        },
        { 
            "time" : "00:07:00",
            "value" : 0
        },
        { 
            "time" : "00:08:00",
            "value" : 0
        },
        { 
            "time" : "00:09:00",
            "value" : 0
        },
        { 
            "time" : "00:10:00",
            "value" : 0
        },
        { 
            "time" : "00:11:00",
            "value" : 0
        },
        { 
            "time" : "00:12:00",
            "value" : 0
        },
        { 
            "time" : "00:13:00",
            "value" : 0
        },
        { 
            "time" : "00:14:00",
            "value" : 0
        },
        { 
            "time" : "00:15:00",
            "value" : 0
        },
        { 
            "time" : "00:16:00",
            "value" : 0
        },
        { 
            "time" : "00:17:00",
            "value" : 0
        }
        ],
        "datasetInterval" : 1,
        "datasetType" : "minute"
    }
}

I need the value of the dateTime in the first JSON object and then the values of the time and value items in the second object. I have implemented the below code however it keeps on giving me a NullReferenceException.

These methods are used in order to help parse the JSON objects

public class RootObject
{
    public Activity activity { get; set; }
    public ActivityGranular activity_granular { get; set; }
}

public class Activity
{
    public string dateTime { get; set; }
    public string value { get; set; }
}

 public class ActivityGranular
{
    public List<ActivityGranularDatapoint> dataset { get; set; }
    public int datasetGranularity { get; set; }
    public string datasetGranularityType { get; set; }
}

public class ActivityGranularDatapoint
{
    public string time { get; set; }
    public int value { get; set; }
}

MainCode in the Main Class which when executed returns null in both root elements in the root objects class above and gives a NullReferenceExceptions

resultsJSON.Replace("-", "_");

root = JsonConvert.DeserializeObject<RootObject>(resultsJSON);

activity = root.activites_steps;
activityGranular = root.activities_steps_intraday;

for (int a = 0; a < activityGranular.dataset.Count; a++)
{
    activityGranularDatapoint[a].time = activityGranular.dataset[a].time;
   activityGranularDatapoint[a].value = activityGranular.dataset[a].value;
}

All help is much appreciated :)

How are you posting the data? Can we see the AJAX call and the endpoint either WebAPI or in your controller? — ZeroBased_IX
– ZeroBased_IX, Commented Feb 10, 2016 at 19:43
I am using HttpRequest to the Fitbit API and storing the response in a WebResponse variable. I am then using a Stream reader to read the response string into the resultsJSON string — Jake Azzopardi
– Jake Azzopardi, Commented Feb 10, 2016 at 19:55
I want to read the dateTime value in the first object and then iterate through every time and value item in the second object — Jake Azzopardi
– Jake Azzopardi, Commented Feb 10, 2016 at 20:01

CodeNotFound · Accepted Answer · 2016-02-10 21:16:14Z

Just use the JsonProperty attribute if the name of a property into your json doesn't respect your needs. Just don't use:

a workaroung or hacking the json data.
don't replace any content of the json
Let it as it is.

The below code just work by renaming properties of your classes as follow

public class RootObject
{
    [JsonProperty("activities-steps")]
    public List<Activity> ActivitesSteps { get; set; }

    [JsonProperty("activities-steps-intraday")]
    public ActivityGranular ActivitiesStepsIntraday { get; set; }
}

public class Activity
{
    [JsonProperty("dateTime")]
    public string DateTime { get; set; }

    [JsonProperty("value")]
    public string Value { get; set; }
}

public class ActivityGranular
{
    [JsonProperty("dataset")]
    public List<ActivityGranularDatapoint> DataSet { get; set; }

    [JsonProperty("datasetInterval")]
    public int DatasetInterval { get; set; }

    [JsonProperty("datasetType")]
    public string DatasetType { get; set; }
}

public class ActivityGranularDatapoint
{
    [JsonProperty("time")]
    public string Time { get; set; }

    [JsonProperty("value")]
    public int Value { get; set; }
}

Ori Refael · Accepted Answer · 2016-02-10 20:19:21Z

0

Please keep in mind that the fields in the json need to match exactly to the Class's fields. for example, RootObject should look like:

class RootObject{
public List<Activity> activitiessteps
public List<Dataset> activitiesstepsintraday
//and so on..
}

Dataset should be:

class Dataset {
public List<Activity> dataset
}

edited Feb 10, 2016 at 20:19

answered Feb 10, 2016 at 20:10

Ori Refael

3,0264 gold badges42 silver badges71 bronze badges

Comments

user5606561 · Accepted Answer · 2016-02-10 20:24:43Z

The objects definitions and JSON do not match, and the Replace method is not correct.

// Replace does not replace the values in the original variable, 
// it returns a string representing the original with the replaced values,
// so you must reassign it to a variable as such.

resultsJSON = resultsJSON.Replace("-", "_");

Assuming you are using the Newtonsoft.Json library, to resolve your issue with matching the signatures it is possible to use the DataContract attributes to rename your class properties without using the Replace method.

As such the following modifications will resolve the null issue based on the JSON you provided.

[DataContract]
public class RootObject
{
    [DataMember(Name = "activities-steps")]
    public Activity[] activity_steps { get; set; }
    [DataMember(Name = "activities-steps-intraday")]
    public ActivityGranular activity_granular { get; set; }

}

public class Activity
{
    public string dateTime { get; set; }
    public string value { get; set; }
}

[DataContract]
public class ActivityGranular
{
    public List<ActivityGranularDatapoint> dataset { get; set; }
    [DataMember(Name = "datasetInterval")]
    public string datasetGranularity { get; set; }
    [DataMember(Name = "datasetType")]
    public string datasetGranularityType { get; set; }
}

public class ActivityGranularDatapoint
{
    public string time { get; set; }
    public int value { get; set; }
}

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