Deserialize json which has a string and complex object

Question

Hi, I am trying to deserialize a json string and write its content into a datatable. I have the following json string with either a string or custom object and not sure how to parse between the string and custom object to write data to the datatable. Running into error NullReference Exception (Object reference not set to an instance of an object) when I deserialize the json.

JSON

{
   "events": [
      {
         "Id": 456895,
         "Name": "Chelsea - Arsenal",
         "BetOffers": {
            "BetType": "Game",
            "Pick": "1",
            "Odds": 1.15
         }
      },
      {
         "Id": 456879,
         "Name": "Liverpool - Manchester United",
         "BetOffers": {
            "BetType": null,
            "Pick": "1",
            "Odds": null
         }
      },
      {
         "Id": 9101112,
         "Name": "Arsenal - Manchester United",
         "BetOffers": {
            "BetType": null,
            "Pick": "1",
            "Odds": null
         }
      },
      {
         "Id": 13141516,
         "Name": "Liverpool - Chelsea",
         "BetOffers": "not accepting"
      },
      {
         "Id": 123456,
         "Name": {
            "game": "Chelsea - Liverpool",
            "gameurl": "http://game.com/api/game/adfgfm"
         },
         "BetOffers": {
            "BetType": "Game",
            "Pick": "1",
            "Odds": 1.15
         }
      }
   ]
}

C#

public class Event
{
    public int Id { get; set; }
    public string Name { get; set; }
    public BetOffer BetOffers { get; set; }
}
public class BetOffer
{
    public string BetType { get; set; }
    public string Pick { get; set; }
    public double? Odds { get; set; }
}
public class MyRootObject
{
    public List<Event> events { get; set; }
}

        try
        {
            string jsonstring = "{\"events\":[{\"Id\":456895,\"Name\":\"Chelsea - Arsenal\",\"BetOffers\":{\"BetType\":\"Game\",\"Pick\":\"1\",\"Odds\":1.15}},{\"Id\":456879,\"Name\":\"Liverpool - Manchester United\",\"BetOffers\":{\"BetType\":null,\"Pick\":\"1\",\"Odds\":null}}]}";; //sample json
            var root = JsonSerializer.Deserialize<MyRootObject>(jsonstring);

            string connectionString = "";

            DataTable dt = new DataTable();
            dt.Columns.Add(new DataColumn("ID", typeof(string)));
            dt.Columns.Add(new DataColumn("Name", typeof(string)));
            dt.Columns.Add(new DataColumn("BetType", typeof(string)));
            dt.Columns.Add(new DataColumn("Pick", typeof(string)));
            dt.Columns.Add(new DataColumn("Odds", typeof(string)));
            DataRow dr = dt.NewRow();

            for (int i = 0; i < root.events.Count; i++)
            {
                    dr = dt.NewRow();
                    dr["ID"] = root.events[i].ID;
                    dr["Name"] = root.events[i].Name;
                    dr["BetType"] = (root.events[i].BetOffers.BetType ?? (object)DBNull.Value);;
                    dr["Pick"] = root.events[i].BetOffers.Pick;
                    dr["Odds"] = (root.events[i].BetOffers.Odds ?? (object)DBNull.Value);;
                    dt.Rows.Add(dr);
            }
}

Could you please guide me how to deserialize jagged json arrays.

Thank you

Answer 1

I got no error running your code other than the incorrect casing of ID -> Id at line 36.

https://dotnetfiddle.net/Ix9vVv

Answer 2

Hi RajD-9527,
Based on your code, there are some errors you need to note.
In your C# code:
You need to change dr["ID"] = root.events[i].ID to dr["ID"] = root.events[i].Id;
In your JSON:

 "BetOffers": "not accepting"  

There are three attributes in BetOffers , so you need to clearly specify the attributes and corresponding values.

 "Name": {  
             "game": "Chelsea - Liverpool",  
             "gameurl": "http://game.com/api/game/adfgfm"  
          },  

There is no game or gameurl attribute in Name.
After correcting these errors, I tested your code(include jsonstring and JSON file) and it worked fine.
Test code:

//  string jsonstring = "{\"events\":[{\"Id\":456895,\"Name\":\"Chelsea - Arsenal\",\"BetOffers\":{\"BetType\":\"Game\",\"Pick\":\"1\",\"Odds\":1.15}},{\"Id\":456879,\"Name\":\"Liverpool - Manchester United\",\"BetOffers\":{\"BetType\":null,\"Pick\":\"1\",\"Odds\":null}}]}"; ; //sample json  
string jsonString = File.ReadAllText(@"C:\Users\Desktop\Test.json");  
var root = JsonSerializer.Deserialize<MyRootObject>(jsonString);  

Best Regards,
Daniel Zhang

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