public CalcViewModel()
{
_model = new CalculatorModel();
this.AddSymbolCommand = new Command<string>(symbol =>
{
//for first button press
if (string.IsNullOrEmpty(displayString))
{
if (char.IsDigit(symbol[0]))
{
DisplayString += symbol;
return;
}
else
return;
}
//constraint for input only two numbers and action symbol
if (!char.IsDigit(symbol[0]) && symbol != "." && CommandIsFull(displayString))
return;
char lastSymbol = GetLastSymbol(displayString);
//check point enter
if (symbol == "." && !CanAddPoint(displayString, lastSymbol))
return;
//check re-enter mathoperator
else if (!Char.IsDigit(symbol[0]) && !CanAddMath(displayString, lastSymbol))
{
DisplayString = ReplaceLastSymbol(displayString, symbol);
return;
}
DisplayString += symbol;
});
this.RemoveLastSymbolCommand = new Command(obj =>
{
if (!string.IsNullOrEmpty(displayString))
this.DisplayString = displayString.Substring(0, displayString.Length - 1);
});
this.ClearAllCommand = new Command(obj => { this.DisplayString = string.Empty; });
this.CalculateCommand = new Command(obj =>
{
var result = _model.Calculate(displayString);
if (result != null)
DisplayString = result.ToString();
});
}
