Error in IDictonary, please help me sir

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.IO;
namespace Clustering_Test
{
    class Program
    {
        static int T24, T3, T4;
        static void Main(string[] args)
        {
            IDictionary<string, IDictionary<string, IDictionary<string, int>>> Region = new Dictionary<string, IDictionary<string, IDictionary<string, int>>>();
            // Reading input text file
            string dirFile = @"C:\FileDir\SAMPLE_INPUT2.txt";
            string recLine;
            int recCounter = 0;
            StreamReader srTable = new StreamReader(dirFile);
            while ((recLine = srTable.ReadLine()) != null)
            {
                recCounter++;
                if (recCounter < 3) continue;
                ParseLine(recLine, Region);
            }
            Dump(Region);
            Console.ReadKey();
        }
        private static void ParseLine(string recLine, IDictionary<string, IDictionary<string, IDictionary<string, int>>> Region)
        {
            if (recLine.Trim() == String.Empty)
                return;
            try
            {
                string main_area = recLine.Substring(0, 11).Trim();
                string cluster = recLine.Substring(12, 11).Trim();
                string excDays = recLine.Substring(24, 16).Trim();

                // adding cluster type key
                if (!Region.ContainsKey(main_area))
                    Region[main_area] = new Dictionary<string, IDictionary<string, int>>();
                // adding cluster name key
                if (!Region[main_area].ContainsKey(cluster))
                {
                    Region[main_area][cluster] = new Dictionary<string, int>();
                    Region[main_area][cluster][excDays] = 0;
                }

                // summing up total
                if (Region[main_area].ContainsKey(cluster))
                 Region[main_area][cluster][excDays] += 1;
                int excDays2 = Convert.ToInt32(excDays);
                if (excDays2 < 2)
                    T24++;
                else if (excDays2 > 1 && excDays2 < 4)
                    T3++;
                else if (excDays2 > 3)
                    T4++;

            }
            catch (Exception e)
            {
                Console.Error.WriteLine("Failed to parse line \"{0}\", {1}", recLine, e.Message);
            }
        }
        private static void Dump(IDictionary<string, IDictionary<string, IDictionary<string, int>>> main_area)
        {
            foreach (string MainArea in main_area.Keys)
            {
                foreach (string Cluster in main_area[MainArea].Keys)
                {
                    foreach (string ExcDays in main_area[MainArea][Cluster].Keys)
                    {
                        Console.WriteLine("There are {0} {1} {2} named {3}", main_area[MainArea][Cluster][ExcDays], ExcDays, Cluster, MainArea);
                    }
                }
            }
            Console.WriteLine();
            Console.WriteLine("Total 24hrs:   {0} ", T24);
            Console.WriteLine("Total 3days:   {0} ", T3);
            Console.WriteLine("Total 4days:  {0} ", T4);
        }
    } // End class
} // End namespace