wpf viewmodel first approach - multiple instances of same usercontrol in same view.

Question

Hi,

We are folllowing mvvm approach for a wpf application.

We have are following view-model approach..I mean we create view-models and map them using

 <DataTemplate DataType="{x:Type vm:CityViewModel}">
        <vw:Cities/>
    </DataTemplate>

In this city - view ..I have a user control...which I am using multiple times...

<view:UserControl1 Grid.Row="2" DataContext="{Binding UcViewModel}" Margin="291,5,291,-5"></view:UserControl1>
<view:UserControl1 Grid.Row="3" DataContext="{Binding Uc2ViewModel}" ></view:UserControl1>

We create multple instances of user control view model inside CityViewmodel.

Does this approach comply with mvvm ???

Answer 1

I would consider the MVVM pattern to be a loose guide.

Ideally what you are looking for is a testable application. Any code in the UI is harder to test.

If this works in you circumstances then go for it, but keep testability in mind.

In an application I am working on at the moment I have an ItemsControl with 6 instances of the same UserControl and ViewModel.

Edit:

public class InsuranceViewModel 
{
  public ObservableCollection<UnderwritingViewModel> Underwriting { get; set; }
}

In the view I have:

<ItemsControl ItemsSource="{Binding Path=Underwriting}">
  <ItemsControl.ItemTemplate>
    <DataTemplate>
      <!-- this could be another UserControl -->
      <views:UWView DataContext="{Binding}" />

      <!-- or a full data template defined in this view -->
    </DataTemplate>
  </ItemsControl.ItemTemplate>
</ItemsControl>

Or you could put this in your resources:

So, in effect, all you have to do is create new ViewModel instances in your DataContext and the template will take care of the View creation.