string input = "abacadaeee";

Dictionary<char, int> letterCount = new Dictionary<char, int>();

foreach(char letter in input){
	if(!(letterCount.ContainsKey(letter)))
		letterCount.Add(letter, 0);
	if(letterCount.ContainsKey(letter))
		letterCount[letter] += 1;
}

foreach(KeyValuePair<char, int> entry in letterCount)
{
	Console.WriteLine(entry.Key +" : "+ entry.Value);
}