Silverlights Dataform with MVVM and WCF Ria Services

1
votes

Good evening,

I am looking for someone to help me with my understanding of how to incorporate the Silverlight DataForm with my ViewModel that using WCF Ria Services. What I am trying to accomplish is using the DataForm manage my collection of entity and utilize its built in navigation, Add, Edit and Delete functionality. Howerver, I am having trouble tying it all together with my ViewModel and Ria Services.

From my understanding, the DataForm needs to be bound to an ObservableCollection<T>. However when I query from the WCF Ria Service context. ie. 

_context.Load(_context.GetAllCustomersQuery(), loadCustomersQueryCallback, true);

I will receive back an IQueryable in the callback method, which i would have to cast as an ObservableCollection<T> like so?

Customers = new ObservableCollection<Customer>(_context.Customers);

Customers is a property in my ViewModel like so...

    public ObservableCollection<Customer> Customers
    {
        get { return _customers; }
        set
        {
            if (_customers != value)
            {
                _customers = value;
                OnPropertyChanged("Customers");
            }
        }
    }

The DataForm is bound to the Customers Property of the ViewModel and I am able to see the data from my datasource, I can navigate between entities, I can edit an existing entity and persist the changes back to the database however I cannot add or delete entites.

Is what I'm doing with the Customers property correct? have I "disconnected" from the context by casting into a new ObservableCollection and therefore have not actually added or removed the entities from the context?

Any help is greatly appreciated.

Regards,

2
silverlightmvvmwcf-ria-servicesdataform

2 Answers

3
votes

I think you hit on the issue in your last question. When you create a new ObservableCollection, you've disconnected from collection change tracking (adds and deletes). Instead of using OC, there are a number of other options worth considering. In your case, it looks like EntitySet or EntityList may be the best options. For a full rundown of these types, take a look at my post on collection binding in RIA Services SP1.

0
votes

You could use :

Customers.Clear(); // Or dispose every customer if it is Disposable
Customers = new ObservableCollection(result.ToList());