private void TypeSelection(object sender, RoutedEventArgs e)
        {
            var form = new ResourceTypeSelection(manager, resource);

            form.ShowDialog();
            if (resource.Type == null)
            {
                resTypeName.Text       = "Tip: Niste izabrali tip!";
                resTypeName.Foreground = Brushes.Red;
                return;
            }
            resTypeName.Text       = "Tip: " + resource.Type.Name;
            resTypeName.Foreground = Brushes.Black; // bug ako je null tip
        }
        private void ResourceTypePicker(object sender, RoutedEventArgs e)
        {
            Resource resource      = dgrMain.SelectedItem as Resource;
            Resource fake_resource = new Resource();

            if (resource == null)
            {
                MessageBox.Show("Morate prvo odabrati resurs", "Greška",
                                MessageBoxButton.OK, MessageBoxImage.Error);
                return;
            }
            fake_resource.Type = resource.Type;
            var form = new ResourceTypeSelection(manager, fake_resource);

            form.ShowDialog();

            resType.Text      = "Tip: " + fake_resource.Type.Name;
            new_resource_type = fake_resource.Type;
        }