using Newtonsoft.Json.Linq;
public static void Main()
JArray gctSheetSpreadJs = new JArray();
JArray colGCTArray = new JArray();
gctSheetSpreadJs.Add(colGCTArray);
var cellGct = JObject.Parse($"{{'cell':'{i}_{j}'}}");
colGCTArray.Add(cellGct);
Console.WriteLine(Newtonsoft.Json.JsonConvert.SerializeObject( gctSheetSpreadJs, Formatting.Indented ));