Frequency in string

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace filing
{
    public struct alphabet
    {
        public char value;
        public int frequency;

    }
    class Program
    {
        static void Main(string[] args)
        {

            string s = Console.ReadLine();
            alphabet[] word = new alphabet[s.Length];
            System.IO.FileStream fs = new System.IO.FileStream("C:\\Users\\ABD\\Desktop\\input.txt", System.IO.FileMode.OpenOrCreate);
            System.IO.BinaryWriter bw = new System.IO.BinaryWriter(fs);

            bw.Write(s);
            bw.Close();

            System.IO.FileStream fs1 = new System.IO.FileStream("C:\\Users\\ABD\\Desktop\\input.txt", System.IO.FileMode.Open);
            System.IO.BinaryReader br = new System.IO.BinaryReader(fs1);
            br.ReadChar();
            string newS = "";
            int j = 0;
            for (int i = 0; i < s.Length; i++)
            {
                char temp = br.ReadChar();
                if (contain(newS, temp) > -1)
                { word[contain(newS, temp)].frequency++;

                }
                else
                {
                    word[j].value = temp;
                    word[j].frequency = 1;
                    newS += temp;
                    j++;
                }
            }

            for(int i = 0; i<j; i++)
            {
                Console.WriteLine("Value = {0}\tFrequency = {1}", word[i].value, word[i].frequency);

            }
        }
        public static int contain(string s, char c)
        {
            int pos = -1;
            for(int i = 0; i < s.Length; i++)
            {
                if (s[i] == c)
                    pos = i;

            }
            return pos;



        }
    }
}