Question

I have a service returning an array of type BaseItem. BaseItem has N subtypes. I’m consuming this service in my WPF application (Prism, MVVM) from a view model. In the constructor of this view model I populate an observable collection of type BaseItem:

public CurrentViewModel(IDataService dataService) 
{ 
    _dataService = dataService

    var baseItems = _dataService.GetAllItems(); // there are many kinds of BaseItems
    _baseItems = new ObservableCollection<BaseItem>(baseItems.ToList()); 
} 

So far so good. In my CurrentView I have an ItemsControl that binds to this collection. In this control I want to render each BaseItem by using another View (and its view model).

Until now, I can’t use DataTemplateSelector because I can’t define each DataTemplate in it, I’m loading N modules (which contain classes which inherit from BaseItem) and PRISM loads them dinamically from an specific folder.

I’m using view Model first approach, what other alternatives do I have to implement the scenario?

Answer 1

simply export your datatemplate resources as a resourcedictionary from your moduls with the specific subtype as DataType. i do this with MEF and in my main app merge this resourcedictionarys. now all datatemplates/views are known to WPF and the itemscontrol render every subtype viewmodel like you want.

EDIT:

modul1.dll

public class Modul1VM : BaseItemViewModel {} 

ResourceDictionary in modul1.dll exported with MEF

<DataTemplate DataType="{x:Type local: Modul1VM}">
 <view:Yourmodul1View/>
</DataTemplate>

modul2.dll

public class Modul2VM : BaseItemViewModel {} 

ResourceDictionary in modul2.dll exported with MEF

<DataTemplate DataType="{x:Type local: Modul2VM}">
 <view:Yourmodul2View/>
</DataTemplate>

your main app

• merge alle exported Resourcedictionarys

app.xaml.cs

 [ImportMany("Resourcen", typeof (ResourceDictionary))] 
 private IEnumerable<ResourceDictionary> _importResourcen;

OnStartup

 foreach (var resourceDictionary in _importResourcen)
 {
     this.Resources.MergedDictionaries.Add(resourceDictionary);
 }

your itemscontrol just need the collection of BaseItemViewModels as itemssource