public static int IndexOf(string str, char value)
        {
            if (str == null || value == '\u0000')
            {
                throw new ArgumentNullException("Input cannot be empty. Please try again!");
            }

            else
            {
                int position = 0;

                for (int i = 0; i < str.Length; i++)
                {
                    if (value == str[i])
                    {
                        position = i;
                        return position;
                    }
                }
                return -1;
            }

        }