Ok, after looking at your code, AND the other replies, there are areas that do have real problems. LOGICAL ERROR: public string acctype { get { return _acctype; } set { if (_acctype = "savings" || _acctype = "current") { _acctype = value; } else { _acctype = ""; } } } In your test, you are assigning the strings to _acctype, what you accomplish will not be what you want, as _acctype will always be assigned the contents of value. QUESTIONABLE on what you are attempting to do: public int credit(_balance , _amount) { return _balance + _amount; } public int debit(_balance , _amount) { return _balance - _amount; } you are overriding the internal private class variables _balance and _amount with what you pass in as _balance and _amount. Im not sure what you intended to do here. Is the class variable _amount needed? Are you trying to update _balance, or are you just attempting to deliver the would be changes just for the values or to update externally? -Later! -WB-