Question

I am really stuck trying to implement RIA Services with MVVM and a crud datagrid. I think i’m missing some key idea. All of the examples I have seen use a submit button or similar to send the data back to the client. I’d rather submit as soon as a row is added/deleted/modified. I thought of a couple of approaches:

• Have my IEnuerable Itemsource property automatically bound to my context’s entitycontainer. I tried this but I cant set the context’s entities from the property.
• Capture the row change events and manually tell my context that is has changed items. This doesnt feel right though in a MVVM design considering my Commodity property should reflect changes in the datagrid.

Additionally, how do I tell RIA Services what method it should be using for a particular crud operation? Does this happen on the client or server?

Note I am using the ComponentOne datagrid, though I dont think its behaviour would differ from the normal Silverlight datagrid for this simple example.

View:

<c1grid:C1DataGrid x:Name="C1Grid"                                    AutoGenerateColumns="False"
ItemsSource="{Binding Commodities}">
<c1grid:C1DataGrid.Columns>
<c1grid:DataGridTextColumn Binding="{Binding Name, Mode=TwoWay}"></c1grid:DataGridTextColumn> 
</c1grid:C1DataGrid.Columns>
</c1grid:C1DataGrid>

ViewModel:

public class CommodityViewModel : Model
    {
        private CommodityContext _context;
        private Commodity _selectedCommodity;

        public IEnumerable<Commodity> Commodities
        {
            get { return _context.Commodities;}
            //Setter wont work here

        }

        public CommodityViewModel()
        {

            _context = new CommodityContext();
            _context.Load(_context.GetCommoditiesQuery(), (LoadOperation<Commodity> loadOperation) =>
            {
                RaisePropertyChanged("Commodities");
                _context.Commodities.EntityAdded += Commodities_EntityAdded;

            }, null );

        }

        private void Commodities_EntityAdded(object sender, EntityCollectionChangedEventArgs<Commodity> e)
        {
            //how does RIA know to use my AddCommodity method on the server side? Where do I set this?
            _context.SubmitChanges();
        }



    }

Answer 1

Ok so perhaps my answer is only relevant to users of the C1 DataGrid – but they have implemented a special API for interacting with RIA Services. Details available here.