DataTableToJson

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Newtonsoft.Json.Linq;

namespace MyProject.Controllers
{
    public class MainController : Controller
    {
        private string DataTableToJson(DataTable dt)
        {
            if (dt == null)
            {
                return "[]";
            };
            if (dt.Rows.Count < 1)
            {
                return "[]";
            };

            JArray array = new JArray();
            foreach (DataRow dr in dt.Rows)
            {
                JObject item = new JObject();
                foreach (DataColumn col in dt.Columns)
                {
                    item.Add(col.ColumnName, dr[col.ColumnName]?.ToString());
                }
                array.Add(item);
            }

            return array.ToString(Newtonsoft.Json.Formatting.Indented);
        }

        public string GetData(string Key,string Data)
        {
            return DataTableToJson(Helpers.DBHelper.ExecuteQuery("SELECT * FROM INBOX"));
        }
    }
}