MVVM light: Pass object from view to viewmodel

Question

I \'ve recently started working with WPF using MVVM light and I have the following (simple scenario).

1. MainWindow contains a listbox of elements.

Answer 1

"I did some step-by-step debugging and the ViewModel constructor seems never to be reached."

Make sure that you are actually binding your view to your view model using one of the following:

In CodeBehind

var showReservoir = new ReservoirViewerView();
showReservoir.DataContext = ViewModelLocator.ReservoirViewerViewModel; //static property
//OR showReservoir.DataContext = new ReservoirViewerViewModel();
showReservoir.Show();

In Xaml View

In Xaml Resources

"What I need is that the new ViewModel (ReservoirViewerViewModel) can somehow get hold of the passed object through the message so that I can then display the details of this object on the child window."

Simply register for the same message in your ReservoirViewerViewModel class:

Messenger.Default.Register(this, (msg) =>
{
    var reservoir = msg.Reservoir;
});

FYI, if you derive your message class from GenericMessage<[content type]> instead of MessageBase, then you can use the already-defined Content property of the GenericMessage class. For example:

public class LaunchShowReservoirMessage: GenericMessage
{
    public LaunchShowReservoirMessage(Reservoir content) : base(content) { }
}

And then:

Messenger.Default.Register(this, (msg) =>
{
    var reservoir = msg.Content;
});