Getting System.Byte [] instead of ASCII value

I'm a newer programmer with C#. I am having an issue where my character frequency reading program is not displaying the ASCII values correctly. What it is supposed to do is read from a text file, convert all uppercase to lowercase, display the ASCII values, frequency appeared, and percentage of the total number of characters each character appears in the file and then sort the list by frequency. Below is my code so far:

using System;
using System.Collections.Generic;
using System.Collections;
using System.Text;
using System.IO;
using LibUtil;
using LibDate;

namespace Ch8Prb3
{
  class Program
  {
    const string INPUT_FILE_NAME = "\\CIS210\\Ch8Prb3\\TextDat.Txt";
    const string OUTPUT_FILE_NAME = "\\CIS210\\Ch8Prb3\\Ch8Prb3Rpt.Txt";

    int count;
    static StreamReader fileIn;
    static StreamWriter fileOut;

    static void Main()
    {
      ConsoleApp.ClrScr(); IdentifyApplication();
      OpenFiles(); LetterFreq();
      CloseFiles();
    }

    static void IdentifyApplication()
    {
      Console.WriteLine();
      Console.WriteLine("Application: Ch8Prb3 -- Find and display a character-frequency  ");
      Console.WriteLine("                        report of only letter chracters and their");
      Console.WriteLine("                        ASCII values from a text file.");
      Console.WriteLine();
    }

    static void OpenFiles()
    {
      try
      {
        fileIn = File.OpenText(INPUT_FILE_NAME);
        Console.WriteLine("{0} was opened", INPUT_FILE_NAME);
      }
      catch
      {
        Console.WriteLine("Error: {0} does not exist\n", INPUT_FILE_NAME);
        ConsoleApp.Exit();
      }

      try
      {
        fileOut = File.CreateText(OUTPUT_FILE_NAME);
        Console.WriteLine("{0} was created\n", OUTPUT_FILE_NAME);
      }
      catch
      {
        Console.WriteLine("Error: {0} could not be created\n", OUTPUT_FILE_NAME);
        ConsoleApp.Exit();
      }
    }

    static void LetterFreq()
    {
      int[] c = new int[(int)char.MaxValue];
      int total = 0;
      int j = 0;

      string s = File.ReadAllText("\\CIS210\\Ch8Prb3\\TextDat.Txt");
      string l = Convert.ToString(Encoding.ASCII.GetBytes(s));

      s = System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo.ToLower(s.ToLower());      
      double percent;

      foreach (char t in s)
      {
        c[(int)t]++;
      }

      PrintHeader();

      for (int i = 0; i < (int)char.MaxValue; i++)
      {
        if (c[i] > 0 && char.IsLetter((char)i))
        {
          total += c[i];
          percent = c[i] / total * 100;          
          fileOut.WriteLine("  {0}  {1,3}  {2,3}  {3,2:f2}", (char)i, l, c[i], percent);
        }        
      }

      fileOut.WriteLine();
      fileOut.WriteLine("Number of Characters: {0}", total);
    }   

    static void PrintHeader()
    {
      fileOut.WriteLine("   Chapter 8 Problem 3");
      fileOut.WriteLine("Character Frequency Report");
      fileOut.WriteLine("      {0:MM/dd/yyyy}", Date.Today);
      fileOut.WriteLine();
      fileOut.WriteLine("      ASCII               ");
      fileOut.WriteLine("Char  Value  Freq  Percent");
      fileOut.WriteLine("----  -----  ----  -------");
    }

    static void CloseFiles()
    {
      fileIn.Close(); fileOut.Close();
    }
  }
}

Instead of getting the ASCII value of each character, I'm getting System.Byte [] all the way down the ASCII column.

Help!