Print Index Of Each Letter In A Word

using System;
class PrintIndexOfEachLetterInAWord
{
  static void Main()
  {
    //Write a program that creates an array containing all letters from the alphabet (A-Z). Read a word from the console and print the index of each of its letters in the array.

    //Read the input word from the console
    string wordToSearch = Console.ReadLine(),
           word = wordToSearch.ToLowerInvariant();//Make all letters small

    //Create the alphabet array (small letters)
    char [] alphabet = new char [26];
    alphabet[0] = 'a';
    for (int i = 1; i < alphabet.Length; i++)
    {
      alphabet[i] = (char)(alphabet[i - 1] + 1);
    }

    //Find each letter from the word with a binary search algorithm and output its index
    foreach (char letter in word)
    {
      int startSearchIndex = 0,
          endSearchIndex = alphabet.Length-1,
          currentMiddle = 0;
      bool foundFlag = false;

      while (startSearchIndex <= endSearchIndex)
      {
        currentMiddle = (startSearchIndex + endSearchIndex)/2;

        if (alphabet[currentMiddle] == letter)
        {
          Console.WriteLine("The index of the searched letter {0} is: {1}", letter, currentMiddle + 1); //the index is + 1 so that we get the number in the alphabet
          foundFlag = true;
          break;
        }
        else if (alphabet[currentMiddle] < letter)
        {
          startSearchIndex = currentMiddle + 1;
        }
        else
        {
          endSearchIndex = currentMiddle - 1;
        }
      }

    if (foundFlag == false)
      {
        Console.WriteLine("Symbol {0} not found in the array! Are you sure you've typed a word?", letter);
      }
    }
  }
}