letter sequense in a word

That's a bit more difficult, given that letters may be duplicated and the same letter may therefore map to different positions in the word, but this should deal with it:

using System;

class Program
{
   static void Main()
   {
       string word = "hello";
       char[] chars = word.ToCharArray();
       Array.Sort(chars);
       int[] usedIndices = new int[chars.Length];

       for (int i = 0; i < usedIndices.Length ; i++)
       {
           usedIndices[i] = -1;
       }
 
       for (int i = 0; i < chars.Length ; i++)
       {
           int index = -1;
           int index2 = -1; 

           while(true)
           {
             index = word.IndexOf(chars[i], index + 1);
             index2 = Array.IndexOf(usedIndices, index);
             if (index2 == -1)
             {
                usedIndices[i] = index;
                break;
             }      
           } 
                  
           Console.WriteLine("{0} is letter {1} in alphabet and letter {2} in word", chars[i], i + 1, index + 1);
       }

       Console.ReadLine();
   }
}