FrequencyTable.cs

public static class FrequencyTable
{
    public static Dictionary<char, int> Create(string input)
    {
        foreach (char character in input)
        {
            if (frequencyTable.ContainsKey(character))
            {
                frequencyTable[character]++;
            }
            else
            {
                frequencyTable[character] = 1;
            }
        }
    }
}