Technologies
- C# 4.0
- Prism 4 with Unity for DI
- WPF
- MVVM
Preface
There are two projects in my solution, MyApp.Shell and MyApp.ModuleFoo
MyApp.Shell's Unity Bootstrapper
protected override IModuleCatalog CreateModuleCatalog()
{
// Module assemblies are read from a directory.
DirectoryModuleCatalog moduleCatalog = new DirectoryModuleCatalog();
moduleCatalog.ModulePath = @".\Modules";
return moduleCatalog;
}
The project MyApp.ModuleFoo contains a View and a View Model.
The ViewModel
// Somehow, Unity sees this class and registers the type.
public class FooViewModel : ViewModelBaseClass
{
public string FooText
{
get { return "Foo!"; }
}
}
The View
<Label Content={Binding FooText} />
The View's Code-behind
// Unity automatically sees this as Constructor Injection,
// which is exactly what I desire.
public FooView(FooViewModel viewModel)
{
DataContext = viewModel;
...
}
MyApp.FooModule's Initialization
Perhaps registering FooView with the region manager is inadvertently registering FooViewModel with Unity?
public void Initialize()
{
var regionManager = ServiceLocator.Current.GetInstance<IRegionManager>();
regionManager.RegisterViewWithRegion("FooRegion", typeof(FooView));
}
The view correctly displays "Foo!".
Problems
- How do I tell Unity to register only a single instance of FooViewModel?
- Additionally, (and I'm thinking ahead here), how would I tell unity not to register FooViewModel?
Thanks for the help.
Edit:
Added MyApp.FooModule's Initialization code
Edit (Solution):
It turns out RegisterViewWithRegion has two overloads. From Prism's documentation, when the overload I'm using is used, a new instance of the view is created. I'm assuming this also creates a new instance of FooViewModel.
The other overload uses a delegate to resolve FooView. The documentation says this overload is used in the "ViewModel-first" approach. I'm going to make this question as answered, but if anyone has any additional insight, I'd love to hear.
