Using GetEnumerator()

Testing ASCII values of user input

byte[] _asciiAnswer = Encoding.ASCII.GetBytes(AnswerTb.Text.Trim());

IEnumerator _asciiChars = _asciiAnswer.GetEnumerator();
while (_asciiChars.MoveNext())
{
  byte _char = (byte)_asciiChars.Current;
  if (_char >= 65 && _char <= 90)
    IsUpperCase = true;
}