Silverlight child windows in MVVM pattern - silverlight

Question

I am trying to find the right way to get the data from a ChildWindow/popup using a MVVM pattern in Silverlight (3). For example: I have a main page with a data entry form and I want to open a popup with a list of customers. When user selects a customer I want to transfer selected customer into the main page. This is what the (example) code which I am using at the moment:
Main page
public partial class MainPage : UserControl
{
public MainPageViewModel ViewModel { get; private set; }
public MainPage()
{
InitializeComponent();
ViewModel = new MainPageViewModel();
DataContext = ViewModel;
}
private void SearchCustomer_Click(object sender, RoutedEventArgs e)
{
ViewModel.SearchCustomer();
}
}
public class MainPageViewModel: ViewModel
{
private string customer;
public string Customer
{
get { return customer; }
set { customer = value; RaisePropertyChanged("Customer"); }
}
public void SearchCustomer()
{
// Called from a view
SearchWindow searchWindow = new SearchWindow();
searchWindow.Closed += (sender, e) =>
{
if ((bool)searchWindow.DialogResult)
{
Customer = searchWindow.ViewModel.SelectedCustomer.ToString();
}
};
searchWindow.Show();
}
}
Child window
public partial class SearchWindow : ChildWindow
{
public SearchWindowViewModel ViewModel { get; private set; }
public SearchWindow()
{
InitializeComponent();
ViewModel = new SearchWindowViewModel();
DataContext = ViewModel;
}
private void OKButton_Click(object sender, RoutedEventArgs e)
{
DialogResult = ViewModel.OkButtonClick();
}
private void CancelButton_Click(object sender, RoutedEventArgs e)
{
DialogResult = ViewModel.CancelButtonClick();
}
}
public class SearchWindowViewModel: ViewModel
{
private Customer selectedCustomer;
private ObservableCollection<Customer> customers;
public ObservableCollection<Customer> Customers
{
get { return customers; }
set {customers = value; RaisePropertyChanged("Customers"); }
}
public Customer SelectedCustomer
{
get { return selectedCustomer; }
set { selectedCustomer = value; RaisePropertyChanged("SelectedCustomer"); }
}
public SearchWindowViewModel()
{
Customers = new ObservableCollection<Customer>();
ISearchService searchService = new FakeSearchService();
foreach (Customer customer in searchService.FindCustomers("dummy"))
Customers.Add(customer);
}
public bool? OkButtonClick()
{
if (SelectedCustomer != null)
return true;
else
return null; // show some error message before that
}
public bool? CancelButtonClick()
{
return false;
}
}
Is this the right way or is there anything more "simple"?
Cheers,
Rok

Answer 1

More problematic here is the use of View specific terms and types in your VMs. Click events, DialogResults should not be anywhere near your ViewModels.
With regards to the question, I had a similiar question about this here:
Handling Dialogs in WPF with MVVM
The answer I accepted was the use of the Mediator pattern to get around this. Have a look. :)

Answer 2

A good MVVM library which supports opening child window is Chinch mvvm helper library. You can look at a sample at http://www.codeproject.com/KB/silverlight/SL4FileUploadAnd_SL4_MVVM.aspx.