Question

So I have a primary MainViewModel that collects and distributes a fair amount of real-time data (changes every .1 seconds). Currently all of my Controls are referencing my MainViewModel.

I’m using a UserControl Control to replicate many objects of the same type of Digital Gauge.

My question is, is there a best practice for “pushing” or “referencing” data from my MainViewModel to a ControlViewModel? The purpose I have in mind is to keep the DependencyProperties I need tucked away cleanly in a ControlViewModel and keep the MainViewModel as clean and tidy as possible.

Is MVVMLight Messaging an option?
Is an event appropriate?
Can I setup bindings from the ControlViewModel to the MainViewModel so when the MainViewModel data is updated, it gets reflected in the ControlViewModel?

Answer 1

If I understand the question properly, I think you may just want to create a property of that exposes a collection of ControlViewModels in your MainViewModel:

public class MainViewModel : INotifyPropertyChanged
{
    public IEnumerable<ControlViewModel> Controls { get; private set; }
}

You can set this with all of the necessary ControlViewModel objects in the constructor. If you might add or remove gauges, change IEnumerable to ObservableCollection.

Then for your gauges, you’d use an ItemsControl and set ItemsSource="{Binding Controls}". This will automatically make the DataContext for each item one of your ControlViewModels.

To render the items with your gauge control, set the ItemTemplate on the ItemsControl:

<ItemsControl.ItemTemplate>
    <DataTemplate DataType="{x:Type YourNamespace:ControlViewModel}">
        <YourNamespace:DigitalGauge />
    </DataTemplate>
</ItemsControl.ItemTemplate>