private void DataGrid_MouseDoubleClick(object sender, MouseButtonEventArgs e)
        {
            DataGrid dg = sender as DataGrid;

            if (dg == null)
            {
                return;
            }

            Zinsfestschreibung zinsF = (Zinsfestschreibung)dg.SelectedItem;
            if (zinsF == null)
            {
                return;
            }

            var viewModel = new EigenschaftenZinsfestschreibungViewModel(zinsF);

            var window = new EigenschaftenZinsfestschreibungView();
            window.Owner = this;
            window.WindowStartupLocation = System.Windows.WindowStartupLocation.CenterOwner;

            EventHandler handler = null;
            handler = delegate
            {
                viewModel.RequestClose -= handler;
                window.Close();
            };

            viewModel.RequestClose += handler;
            window.DataContext = viewModel;
            window.ShowDialog();
        }
        private void NeuZinszeitraum()
        {
            Zinsfestschreibung zinsfest = new Zinsfestschreibung();

            var viewModel = new EigenschaftenZinsfestschreibungViewModel(zinsfest);

            var window = new EigenschaftenZinsfestschreibungView();
            window.Owner = App.window;
            window.WindowStartupLocation = System.Windows.WindowStartupLocation.CenterOwner;

            EventHandler handler = null;
            handler = delegate
            {
                viewModel.RequestClose -= handler;
                window.Close();
            };

            viewModel.RequestClose += handler;
            window.DataContext = viewModel;
            window.ShowDialog();

            if (viewModel.DialogResult == true)
            {
                kredit.Zinszeitraeume.Add(zinsfest);
            }
        }