/// <summary>
/// calculates the tax owed based on age and salary
/// </summary>
public void CalculateTax(TaxViewModel viewModel)
{
var taxDiscount = _taxReliefBrackets.SingleOrDefault(x => viewModel.Age >= x.Min && viewModel.Age <= x.Max);
viewModel.MonthlyTaxRelief = taxDiscount == null ? 0m : taxDiscount.Discount;
// TODO: do we apply the tax relief before or after computing the tax owed?
var monthlySalary = viewModel.MonthlySalary - viewModel.MonthlyTaxRelief;
viewModel.MonthlyTaxAmount = 0m;
// we could LINQ this but we'd lose some readability...
foreach (var bracket in _taxBrackets)
{
if (monthlySalary <= bracket.Low)
{
break;
}
var taxableAtThisRate = Math.Min(bracket.High - bracket.Low, monthlySalary - bracket.Low);
var taxThisBand = taxableAtThisRate * bracket.Rate;
viewModel.MonthlyTaxAmount += taxThisBand;
}
}
public MainWindow()
{
InitializeComponent();
DataContext = new TaxViewModel();
}