using System;

using System.Text.Json;

using System.Text.Json.Serialization;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var json = @"

        {

          ""value"": {

            ""Description"": ""Total  Calculated things"",

            ""2018"": ""5,820,456 "",

            ""2019"": ""2,957,447 ""

          }

        }";

        var myObj = JsonSerializer.Deserialize<SomeType>(json);

        var result = new WrapperType

        {

            Value = new ProperlyFormattedType()

        };

        foreach (var pair in myObj.Value)

        {

            if (pair.Key == "Description")

            {

                result.Value.Description = pair.Value;

            }

            else if (int.TryParse(pair.Key, out int _))

            {

                result.Value.YearData

                    .Add(new DatedValues

                         {

                             Year = pair.Key,

                             Data = pair.Value

                         });

            }

        }

        Console.WriteLine(JsonSerializer.Serialize(result));

    }

}

​

public class SomeType

{

    [JsonPropertyName("value")]

    public Dictionary<string, string> Value { get; set; }

}

​

​

public class WrapperType

{

    public ProperlyFormattedType Value { get; set; }

}

​

public class ProperlyFormattedType

{

    public string Description { get; set; }

    public List<DatedValues> YearData { get; set; } = new List<DatedValues>();

}

​

public class DatedValues

{

    public string Year { get; set; }

    public string Data { get; set; }

}