c# - Error when deserializing JSON to Object

Question

I need to convert JSON data that I get from a REST API and convert them to CSV for some analytic. The problem is that the JSON data do not necessarily follow the same content, so I can't define a type for mapping. This has become a challenge that is taking too much of my time. I have already created some code, but of course it is not working as it throws exception on this line

var data = JsonConvert.DeserializeObject<List<object>>(jsonData);

The error is:

Additional information: Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[System.Object]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.

To fix this error either change the JSON to a JSON array (e.g. [1,2,3]) or change the deserialized type so that it is a normal .NET type (e.g. not a primitive type like integer, not a collection type like an array or List) that can be deserialized from a JSON object. JsonObjectAttribute can also be added to the type to force it to deserialize from a JSON object.

Path 'data', line 2, position 10.

please let me know what I can do to get this going.

A sample of data would be like this, the fields of data can change very often, for example a new field can be added the next day, so I don't have the liberty to create a .Net class to map the data.

{
  "data": [
    {
      "ID": "5367ab140026875f70677ab277501bfa",
      "name": "Happiness Initiatives - Flow of Communication/Process & Efficiency",
      "objCode": "PROJ",
      "percentComplete": 100.0,
      "plannedCompletionDate": "2014-08-22T17:00:00:000-0400",
      "plannedStartDate": "2014-05-05T09:00:00:000-0400",
      "priority": 1,
      "projectedCompletionDate": "2014-12-05T08:10:21:555-0500",
      "status": "CPL"
    },
    {
      "ID": "555f452900c8b845238716dd033cf71b",
      "name": "UX Personalization Think Tank and Product Strategy",
      "objCode": "PROJ",
      "percentComplete": 0.0,
      "plannedCompletionDate": "2015-12-01T09:00:00:000-0500",
      "plannedStartDate": "2015-05-22T09:00:00:000-0400",
      "priority": 1,
      "projectedCompletionDate": "2016-01-04T09:00:00:000-0500",
      "status": "APR"
    },
    {
      "ID": "528b92020051ab208aef09a4740b1fe9",
      "name": "SCL Health System - full Sitecore implementation (Task groups with SOW totals in Planned hours - do not bill time here)",
      "objCode": "PROJ",
      "percentComplete": 100.0,
      "plannedCompletionDate": "2016-04-08T17:00:00:000-0400",
      "plannedStartDate": "2013-11-04T09:00:00:000-0500",
      "priority": 1,
      "projectedCompletionDate": "2013-12-12T22:30:00:000-0500",
      "status": "CPL"
    }
 ]
}



namespace BusinessLogic
{
    public class JsonToCsv
    {

       public string ToCsv(string jsonData, string datasetName)
       {
          var data = JsonConvert.DeserializeObject<List<object>>(jsonData);
          DataTable table = ToDataTable(data); 
          StringBuilder result = new StringBuilder();

            for (int i = 0; i < table.Columns.Count; i++)
            {
                result.Append(table.Columns[i].ColumnName);
                result.Append(i == table.Columns.Count - 1 ? "
" : ",");
            }

            foreach (DataRow row in table.Rows)
            {
                for (int i = 0; i < table.Columns.Count; i++)
                {
                    result.Append(row[i].ToString());
                    result.Append(i == table.Columns.Count - 1 ? "
" : ",");
                }
            }

            return result.ToString().TrimEnd(new char[] {'
', '
'});

        }

        private DataTable ToDataTable<T>( IList<T> data )
            {
            PropertyDescriptorCollection props = TypeDescriptor.GetProperties(typeof(T));
            DataTable table = new DataTable();
            for (int i = 0 ; i < props.Count ; i++)
                {
                PropertyDescriptor prop = props[i];
                table.Columns.Add(prop.Name, prop.PropertyType);
                }

            object[] values = new object[props.Count];
            foreach (T item in data)
                {
                for (int i = 0 ; i < values.Length ; i++)
                    {
                    values[i] = props[i].GetValue(item);
                    }

                table.Rows.Add(values);
                }

            return table;
            }


        }
}

Answer 1

The real issue here is that you are trying to deserialize into a List<object> but your JSON actually represents a single object containing a data property which then contains a list of objects. That is why you are getting this error. Json.Net can't deserialize a single object into a list. I think what you really want to do is define a container class like this:

class Root
{
    public List<Dictionary<string, object>> Data { get; set;}
}

Then deserialize like this:

var data = JsonConvert.DeserializeObject<Root>(jsonData).Data;

You will then end up with a list of dictionaries, where each dictionary represents one item in the JSON array. The dictionary key-value pairs are the dynamic values in each item. You can then work with these as you would with any other dictionary. For example, here is how you would dump out all the data:

foreach (var dict in data)
{
    foreach (var kvp in dict)
    {
        Console.WriteLine(kvp.Key + ": " + kvp.Value);
    }
    Console.WriteLine();
}

Fiddle: https://dotnetfiddle.net/6UaKhJ