R – Deleting data in Silverlight 3 with .NET RIA Data Services

entity-frameworksilverlight-3.0wcf-ria-services

We're trying to play around with RIA Services. I can't seem to figure out how to delete a record. Here's the code I'm trying to use.

   SomeDomainContext _SomeDomainContext = (SomeDomainContext)(productDataSource.DomainContext);
    Product luckyProduct = (Product)(TheDataGrid.SelectedItem);

    _SomeDomainContext.Products.Remove(luckyProduct);

    productDataSource.SubmitChanges();

The removing the object from the Entity part works fine, but it doesn't seem to do anything to the DB. Am I using the objects like I'm supposed to, or is there a different way of saving things?

Best Answer

The error system is a little finicky. Try this o get the error if there is one and that will give you an idea. My problem was dependencies to other tables needing deletion first before the object could be. Ex: Tasks deleted before deleting the Ticket.

System.Windows.Ria.Data.SubmitOperation op = productDataSource.SubmitChanges();
op.Completed += new EventHandler(op_Completed);

void TicketsLoaded_Completed(object sender, EventArgs e) {
   System.Windows.Ria.Data.SubmitOperation op = (System.Windows.Ria.Data.SubmitOperation)sender;
   if (op.Error != null) {
      ErrorWindow view = new ErrorWindow(op.Error);
      view.Show();
   }
}

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Combining .NET RIA Services and MVVM in Silverlight 3.0

Agree with ChuckJ - generally the DomainContext forms part of a view model. For example, say I had a search page that allowed searching against a product catalog. Here is how I'd structure things:

On the server:

class Catalog : DomainService {
    IQueryable<Product> GetProducts(string keyword) { ... }
}

The generated DomainContext:

class Catalog : DomainContext {
    EntityList<Product> Products { get; }
    void LoadProducts(string keyword);
}

The view model I would write:

class SearchViewModel {
    Catalog _catalog = new Catalog();

    public IEnumerable<Product> Results {
        get { return _catalog.Products; }
    }

    public void Search(string keyword) {
        _catalog.Products.Clear();
        _catalog.LoadProducts(keyword);
    }
}

And then finally in my xaml, I'd set my UserControl's DataContext to be an instance of SearchViewModel, and bind an ItemsControl to the Results property. I'd use the ViewModel pattern of your choice to bind a button click to Search (which is effectively a command that SearchViewModel exposes). I personally like something that I have working with Silverlight.FX as in:

<Button Content="Search"
  fxui:Interaction.ClickAction="$model.Search(keywordTextBox.Text)" />

and as initially shown here.

As Chuck mentions I might indeed have other state in my view model, for example, the SelectedProduct that might be two-way bound to the SelectedItem of a ListBox in my xaml, and then bind the same SelectedProduct as the DataContext of a DataForm to show details of a selected product.

Hope that helps! I'll be blogging about this some more on my blog soon.

Wcf – RIA Services versus WCF Services

.NET RIA Services was created for Silverlight that runs in the browser. Silverlight is running a special version of the the .NET framework and in an N-tier application Silverlight is unable to share assemblies with the server side. By employing some clever code generation .NET RIA Services makes this gap almost invisible to the developer. Classes similar to the domain classes are code generated on the client side, and ways to move objects back and forth between client and server are also made available.

You will probably be able to call into a .NET RIA Service from Windows Mobile, but I don't think it will particular easy and currently you may in fact have to reverse engineer what's sent on the wire (JSON is used). WCF on the other has a much more broad scope, but doesn't support Silverlight development in the same way that .NET RIA Services does.

If you are writing a Silverlight only N-tier application .NET RIA Services are very powerful. If however Silverlight is only one of several clients WCF is probably a better choice.

Please note the .NET RIA Services hasn't been released yet, but a preview is available for download.

Best Answer

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Combining .NET RIA Services and MVVM in Silverlight 3.0

Wcf – RIA Services versus WCF Services

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