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Okay, so I have this Silverlight client program. I'm not allowed to use the web project, but I do need to be able to read from an SQL database for my data.

Some internet searching brought me to LINQ to SQL and the System.Data.Linq.DataContext object, as well as SQLMetal.exe. I have created my data context object from the meta data in a remote SQL database and the code looks okay (from what I can tell - all the right names and types seem to be there).

What I wanted to do was add this into Silverlight, but I realised, on importing the code, that you can't use System.Data in a Silverlight application, which sort of rules out having this code in the Silverlight client itself. Now this is annoying because a DataContext quite conveniently comes with properties which are tables and such like (I find those really convenient in Silverlight).

So I can't do it the 'normal way'. I can do it with a WCF service, but... well, here's where I could use some advice. I can create a WCF service with asynch calls, but I'm not really sure in what way to wire up the DataContext object. I mean... I need access to the classes in there within my Silverlight application (for my entities in the database) (and I'm not quite sure how to do that - help there would be appreciated). Then to synchronise it all up? Well, I could use some suggestions. For example, before, I have an exposed ObservableCollection. In its getter, it repopulated itself with the contents of, for example, Context.Customers. This made things nice and easy, but I can't see a way of doing something like that now. If I made a call to an asynch service for every 'get', surely this would be unacceptably slow.

If you could help me pick my way through this, I would be grateful. Thanks.

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  • You need RIA Services. Commented Nov 29, 2011 at 17:11

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You definitely need to read about Entity Framewrok and couple articles about using WCF RIA + EF in Silverlight applications.

Hope, that will help you.

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This is the .edmx stuff right? I have done this before, but I was able to use the web project part then. I didn't know you could add one of those to the client application only.
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As mentioned above, you can use RIA services.

But more importantly... you should never use the classes that are generated in LINQ to SQL or EF in your client application. Your client application should only know about and use Domain Layer objects. Your datacontext and the types it uses should stay buried behind a repository pattern that gives you back Domain types.

Your client, whatever that may be (Silverlight app, WPF app, etc) only needs to (and should only) use these domain types. This is part of the whole separation of concerns and SOLID principles. Because I can guarantee you at some point in the lifecycle of the app you will swap out your source for data, so you may end up using Entity Framework, or NHibernate to talk to the db instead, in that case your client would be hard-wired to your LINQtoSQL types, and you wouldn't be able to swap out the ORM layer without breaking the client.

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For what it's worth, I'm currently 30K+ LOCs into a complex Silverlight app, and I haven't yet found any value in layering an additional set of classes on top of my EF-generated classes. I understand the theory - just saying that at least sometimes, in practice, it isn't necessary.

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