using System;

using System.Collections.Generic;

using Newtonsoft.Json;

​

public class Program

{

    public static void Main()

    {

        var result = @"{

    ""data"": [{

        ""report_header"": {

            ""c1"": {

                ""name"": ""COLUMN1"",

                ""type"": ""java.lang.String""

            },

            ""c2"": {

                ""name"": ""COLUMN2"",

                ""type"": ""java.lang.String""

            }

        },

        ""report_row"": [{

            ""c1"": ""2019"",

            ""c2"": ""TEST123"",

            ""c3"": ""HERE IS C3""

        }, {

            ""c1"": ""2019"",

            ""c2"": ""TEST345""

        }, {

            ""c1"": ""2020"",

            ""c2"": ""TEST567""

        }]

    }],

    ""message"": [""OK""],

    ""status"": 200

 }";

        var root = JsonConvert.DeserializeObject<RootObject>(result);

        var report_row = root.data[0].report_row;

        foreach (var reportRow in report_row)

            foreach (var row in reportRow)

                Console.WriteLine(row.Key + ", " + row.Value);

    }

​

public class C1

{

    public string name { get; set; }

    public string type { get; set; }

}

​

public class C2

{

    public string name { get; set; }

    public string type { get; set; }

}

​

public class ReportHeader

{

    public C1 c1 { get; set; }

    public C2 c2 { get; set; }

}

​

public class Datum

{

    public ReportHeader report_header { get; set; }

    public List<Dictionary<string, string>> report_row { get; set; }

}

​

public class RootObject

{

    public List<Datum> data { get; set; }

    public List<string> message { get; set; }

    public int status { get; set; }

}

}