using System;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

​

public class Program

{

    public static void Main()

    {

        JArray gctSheetSpreadJs = new JArray();

        for(int i=0;i<3;i++){

            JArray colGCTArray = new JArray();

            gctSheetSpreadJs.Add(colGCTArray);

            for(int j=0;j<2;j++){

                var cellGct = JObject.Parse($"{{'cell':'{i}_{j}'}}");

                colGCTArray.Add(cellGct);

            }

        }

        Console.WriteLine(Newtonsoft.Json.JsonConvert.SerializeObject( gctSheetSpreadJs, Formatting.Indented ));

​

    }

}