public CalculatorViewModel()
{
_storedResult = _currentNumber = 0;
_currentOp = CurrentOperationEnum.NONE;
_clearOnNextNumber = true;
_lastOperationEquals = false;
}
public void ProcessString(string input)
{
// first check for numbers
int curNumber;
if (int.TryParse(input, out curNumber))
{
if (_clearOnNextNumber)
{
_currentNumber = 0;
_clearOnNextNumber = false;
}
_currentNumber = _currentNumber * 10 + curNumber;
}
else if (input == "*")
{
_storedResult = _currentNumber;
_currentNumber = 0;
_currentOp = CurrentOperationEnum.MULTIPLY;
}
else if (input == "-")
{
_storedResult = _currentNumber;
_currentNumber = 0;
_currentOp = CurrentOperationEnum.SUBTRACT;
}
else if (input == "+")
{
_storedResult = _currentNumber + _storedResult;
_currentNumber = 0;
_currentOp = CurrentOperationEnum.ADD;
}
else if (input == "=" && _storedResult.HasValue)
{
double oldCurrent = _currentNumber;
switch (_currentOp)
{
case CurrentOperationEnum.ADD:
_currentNumber = _currentNumber + _storedResult.Value;
break;
case CurrentOperationEnum.MULTIPLY:
_currentNumber = _currentNumber * _storedResult.Value;
break;
case CurrentOperationEnum.SUBTRACT:
_currentNumber = _lastOperationEquals ? _currentNumber - _storedResult.Value : _storedResult.Value - _currentNumber;
break;
}
if (!_lastOperationEquals)
{
_storedResult = oldCurrent;
}
_clearOnNextNumber = true;
}
else if (input == "C")
{
_storedResult = _currentNumber = 0;
_currentOp = CurrentOperationEnum.NONE;
}
// record whether the last operation was an equals
_lastOperationEquals = (input == "=");
// Ensure that the 2 properties are updated in the UI
RaisePropertyChanged("Output");
RaisePropertyChanged("OutputCharArray");
}
