private void okButton_Click(object sender, RoutedEventArgs e)
 {
     if (DataIsOK())
     {
         var financialResource = new FinancialResource(
             titleBox.Text,
             double.Parse(sumBox.Text),
             (Currency)currencyBox.SelectedValue
             );
         if (!financialResource.Equals(FinancialResource))
         {
             FinancialResource = financialResource;
             DialogResult      = true;
         }
         else
         {
             DialogResult = false;
         }
     }
     else
     {
         MessageBox.Show("Some fields are empty or invalid!", "Error", MessageBoxButton.OK, MessageBoxImage.Error);
     }
 }
 public FinanceWindow(FinancialResource financialResource)
 {
     InitializeComponent();
     FinancialResource = financialResource;
     FillData();
 }