Cannot deserialize the current JSON array in MVC App

Question

I am building an MVC app and I am pulling data from an API. However, when I run the app, I get the error below. If I remove the line of code causing the error, then the app runs fine but no data is returned.

Below is the link to the error message screenshot

    public List<DailyEquity> GetDailyChart(string symbol)
    {
        // string to specify information to be retrieved from the API
        string IEXTrading_API_PATH = BASE_URL + "stock/" + symbol + "/chart/1d";

        // initialize objects needed to gather data
        string Dailycharts = "";
        List<DailyEquity> DailyEquities = new List<DailyEquity>();
        httpClient.BaseAddress = new Uri(IEXTrading_API_PATH);

        // connect to the API and obtain the response
        HttpResponseMessage response = httpClient.GetAsync(IEXTrading_API_PATH).GetAwaiter().GetResult();

        // now, obtain the Json objects in the response as a string
        if (response.IsSuccessStatusCode)
        {
            Dailycharts = response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
            var aa = Dailycharts.GetType();
        }

        // parse the string into appropriate objects
        if (!Dailycharts.Equals(""))
        {
            DailyChartRoot dailyroot = JsonConvert.DeserializeObject<DailyChartRoot>(Dailycharts,
            new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });
            DailyEquities = dailyroot.dailychart.ToList();
        }

        // fix the relations. By default the quotes do not have the company symbol
        //  this symbol serves as the foreign key in the database and connects the quote to the company
        foreach (DailyEquity Equity in DailyEquities)
        {
            Equity.symbol = symbol;
        }

        return DailyEquities;
    }

But an error is thrown at:

 // parse the string into appropriate objects
        if (!Dailycharts.Equals(""))
        {
            DailyChartRoot dailyroot = JsonConvert.DeserializeObject<DailyChartRoot>(Dailycharts,
            new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });
            DailyEquities = dailyroot.dailychart.ToList();
        }

"Newtonsoft.Json.JsonSerializationException: 'Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'API_Usage.Models.DailyChartRoot' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly. To fix this error either change the JSON to a JSON object (e.g. {"name":"value"}) or change the deserialized type to an array or a type that implements a collection interface (e.g. ICollection, IList) like List that can be deserialized from a JSON array. JsonArrayAttribute can also be added to the type to force it to deserialize from a JSON array. Path '', line 1, position 1.'"

This is the Model class from the Model folder.

public class DailyChartRoot
  {
    public DailyEquity[] dailychart { get; set; }
  }

public class DailyEquity
{
    public int DailyEquityId { get; set; }
    public string minute { get; set; }
    public float marketaverage { get; set; }
    public float marketnotional { get; set; }
    public float marketnumberoftrades { get; set; }
    public float marketopen { get; set; }
    public float marketclose { get; set; }
    public float markethigh { get; set; }
    public float marketlow { get; set; }
    public float marketvolume { get; set; }
    public float average { get; set; }
    public string symbol { get; set; }
}

This is a sample output from the API:

[{"date":"20190405","minute":"09:30","label":"09:30 AM","high":196.47,"low":196.14,"average":196.271,"volume":2360,"notional":463200.325,"numberOfTrades":26,"marketHigh":196.48,"marketLow":196.14,"marketAverage":196.354,"marketVolume":308339,"marketNotional":60543617.1182,"marketNumberOfTrades":712,"open":196.47,"close":196.21,"marketOpen":196.45,"marketClose":196.217,"changeOverTime":0,"marketChangeOverTime":0},{"date":"20190405","minute":"09:31","label":"09:31 AM","high":196.28,"low":196.07,"average":196.147,"volume":2148,"notional":421324.74,"numberOfTrades":25,"marketHigh":196.289,"marketLow":195.93,"marketAverage":196.113,"marketVolume":210621,"marketNotional":41305476.8289,"marketNumberOfTrades":1018,"open":196.1,"close":196.26,"marketOpen":196.22,"marketClose":196.24,"changeOverTime":-0.0006317795293242263,"marketChangeOverTime":-0.0012273750471088639}

Answer 1

The Exception says the object you're deserializing into does not match what your JSON contains.

Here's what the (formatted) json object looks like:

[
    {
        "date": "20190405",
        "minute": "09:30",
        "label": "09:30 AM",
        "high": 196.47,
        "low": 196.14,
        "average": 196.271,
        "volume": 2360,
        "notional": 463200.325,
        "numberOfTrades": 26,
        "marketHigh": 196.48,
        "marketLow": 196.14,
        "marketAverage": 196.354,
        "marketVolume": 308339,
        "marketNotional": 60543617.1182,
        "marketNumberOfTrades": 712,
        "open": 196.47,
        "close": 196.21,
        "marketOpen": 196.45,
        "marketClose": 196.217,
        "changeOverTime": 0,
        "marketChangeOverTime": 0
    },
    {
        "date": "20190405",
        "minute": "09:31",
        "label": "09:31 AM",
        "high": 196.28,
        "low": 196.07,
        "average": 196.147,
        "volume": 2148,
        "notional": 421324.74,
        "numberOfTrades": 25,
        "marketHigh": 196.289,
        "marketLow": 195.93,
        "marketAverage": 196.113,
        "marketVolume": 210621,
        "marketNotional": 41305476.8289,
        "marketNumberOfTrades": 1018,
        "open": 196.1,
        "close": 196.26,
        "marketOpen": 196.22,
        "marketClose": 196.24,
        "changeOverTime": -0.0006317795293242263,
        "marketChangeOverTime": -0.0012273750471088639
    }
]

You could load the objects directly as a List, by using List<DailyEquity> as the Type for JsonConvert.DeserializeObject<T>

// Parsing directly to a List<>
List<DailyEquity> equities = JsonConvert.DeserializeObject<List<DailyEquity>>(/*put your parameters here*/);

I've setup some test cases for your scenario. The following gets me the Exception:

    public void TestJsonDeserialize()
        {
            string jsonStr = /* your json string here */;

            var jsonObj = JsonConvert.DeserializeObject<DailyEquityRoot>(jsonStr);
        }

Changing the Deserialize type to a List of DailyEquity seems to do the job on my test case:

public void TestJsonDeserialize()
        {
            string jsonStr = /* your json goes here*/;

            var jsonObj = JsonConvert.DeserializeObject<List<DailyEquity>>(jsonStr);

            // Asserting the expected result we get from Deserializing
            Assert.NotEmpty(jsonObj);       // Asserts that the collection is not empty
            Assert.Equal(2, jsonObj.Count); // Asserts that the collection size is 2            

            var dailyEquityRecord = jsonObj.First();    // Let's take a look at the first object in the list
            Assert.NotNull(dailyEquityRecord);  // Asserting that the object has been loaded
            Assert.Equal("09:30 AM", dailyEquityRecord.label);  // Asserting that the label for the first record is as expected
        }

I used the following implementation of your json's class:

public class DailyEquity
        {
            public string date { get; set; }
            public string minute { get; set; }
            public string label { get; set; }
            public float high { get; set; }
            public float low { get; set; }
            public float average { get; set; }
            public int volume { get; set; }
            public float notional { get; set; }
            public int numberOfTrades { get; set; }
            public float marketHigh { get; set; }
            public float marketLow { get; set; }
            public float marketAverage { get; set; }
            public int marketVolume { get; set; }
            public float marketNotional { get; set; }
            public int marketNumberOfTrades { get; set; }
            public float open { get; set; }
            public float close { get; set; }
            public float marketOpen { get; set; }
            public float marketClose { get; set; }
            public float changeOverTime { get; set; }
            public float marketChangeOverTime { get; set; }
        }