Nikhil Kothari's Weblog : MIX10 Talk

MIX10 Talk - Slides and Code

Another exciting MIX ... this post contains references to slides and code for my RIA Services session/demo - the BookClub application...

At MIX10, I presented the Developing with WCF RIA Services Quickly and Effectively talk. For the demos I used a BookClub application - the scenario is a team application for team members to use to share books and browse/search/request shared books.

Book Club - Browsing View Book Club - Bookshelf View

The following are the concepts that the demos and code cover:

CRUD (editing your shared books) using the domain service pattern in the BookShelfService implementation, along with both convention and configuration.
Using LINQ across client and server, and working with EntityQuery object on the client, to implement both filtering and "More"-style paging.
Validation via declarative metadata and imperative rules.
Reference data pattern for implementing lookup comboboxes.
Custom DomainServiceFactory implementation for customizing instantiation of domain services in the application.
Custom authentication service implementation (that authenticates and validates user credentials using a Members table in the data model rather than ASP.NET Membership).
Custom authorization rules (see CustomAuthorizationAttribute, just like validation)
ViewModel pattern, aka MVVM, to complement RIA Services, and how you can design view models starting from your user interface or a sketch of a prototype.
Taking DomainServices to the next level by using presentation model or projected types (see how BookClubDomainService exposes BookInfo entities that is a projection over multiple tables in the underlying data model).
Aggregating data from multiple sources (database and Amazon service) within a single DomainService.
Invoking and using stored procedures within a DomainService.
Implementing Invoke operations, i.e. non-CRUD operations alongside the CRUD pattern (see the RequestBook operation on BookClubService).
Reusing the domain service across different front-end applications and screens. Specifically I had a Windows Phone 7 application that used a regular SOAP interface to the same domain service to access the BookClubService.

Book Club on the Go - Windows Phone 7 application

I tried to approach this sample with an eye toward how a real-world application might be built when using RIA Services, based on my blog post before the talk and some of the comments that were posted. I realized there was way more than enough content, but decided to keep the sample as-is for the purposes of sharing it out.

I’ll be blogging many of these bullets listed above with more details in subsequent individual posts, so stay tuned. However, for now you can browse through the code, and the slide deck to get some sense of the concepts. Note that you’ll need to create the database using the included SQL script, and specify your very own Amazon ID and secret key in web.config to run the samples.

I’m on twitter (@nikhilk) if you’d like to connect and be part of the conversation. As always, comments, as well as questions, are welcome below.

Posted on Sunday, 3/21/2010 @ 10:51 PM | #Silverlight

Comments

John Waters

Posted on 3/22/2010 @ 4:09 PM

Hi Nikhil,
Thanks so much for the talk and the code, it was extremely helpful.
You mentioned there was a bug in the generation of the setter for the entity references, do you have an ETA for when a fix would be available?
Also, I do have a question about lookups, I would love to hear your thoughts on your solution:
Say in your example you have 10 categories, and 100 books. You load your 10 categories up front, and then the user starts paging through the books, which get hooked up to their categories.
Now, imaging, another user creates a new category, and adds 10 books for that new category
Your first user reaches those books, and now doesnt have a match for the new category.
How would you solve that? At the point it is discovered a category is missing, it is too late to fetch it, especially given the async nature of things....
Cheers
John

Nikhil Kothari

Posted on 3/22/2010 @ 6:09 PM

@John
The bug fix would be available in the final v1 release of ria services.

As for your scenario of dynamic categories - it depends on your app, how common such things are - if the data is pretty static, you're set. However if your reference data is actually dynamic, there are probably multiple approaches. Two I can think of right now:
1. For very dynamic scenarios, implement polling, or server "push" - hopefully will be more integrated into ria services.
2. For less dynamic scenarios, detect if there is new reference data by looking at entities that got loaded, and seeing if their references resolve. If they don't you're reference data needs to be refreshed. Even though that will happen in an async manner, when the reference data loads up, things will resolve on the basis of foreign keys.

Slashxxx

Posted on 3/25/2010 @ 10:13 PM

Hey Nikhil, great talk, tyvm!!

I'm trying to run up your app and having trouble with your web service connecting to my sqlexpress database running locally on win7 with a default install.

I manually created the BookClub db using sqlsrv mgmt studio 2008 then executed your supplied script with no errors. Queries are working fine in sql server studio.

The error I get is

"A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)"

Nikhil Kothari

Posted on 4/1/2010 @ 2:38 PM

@foobar

The book club app is _not_ a book club database browser. Most end users don't really care to browse a database in its raw form - they instead want to use an application for its features, and capabilities - eg. searching for books, placing requests, contributing books to the book club etc. The app is specifically meant to point out that building an app shouldn't result in a database browser.

If you as a developer want to browse the database, just browse the database using something like SQL management studio. Or if you're an admin, and want to see the raw view, that is fine too as an app scenario, but this app isn't the one that illustrates that basic CRUD scenario.

Nikhil Kothari

Posted on 4/5/2010 @ 7:21 AM

@John
Here is the code you will need to workaround the bug preventing a settable association property when the associated type is an external reference. To be clear, for the next (RTM) release, the correct code to write is simply adding [ExternalReference] on the server, and having code-generation produce this for you.

In a partial Book class, add the following code:



private EntityRef<Category> _category;

[Association("Category_Book", "CategoryID", "CategoryID", IsForeignKey=true)]

[ExternalReference]

public Category Category {

    get {

        if (_category == null) {

            _category = new EntityRef<Category>(this, "Category", FilterCategory);

        }

        return this._category.Entity;

    }

    set {

        Category previous = Category;

        if (previous != value) {

            if (value != null) {

                this.CategoryID = value.CategoryID;

            }

            else {

                CategoryID = default(int);

            }

        }

    }

}



private bool FilterCategory(global::BookClub.Web.DataModel.Category entity) {

    return (entity.CategoryID == CategoryID);

}

Martin Z

Posted on 4/9/2010 @ 1:02 AM

Hi Nikhik,

Great talk, great demo. I'm trying to get the BookClub app running, but can't get it to work. At build time, I get a warning: "Warning 1 Could not resolve this reference. Could not locate the assembly "Microsoft.ServiceModel.DomainServices.Hosting, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors. BookClub.Web"

I can't find the specified assembly. I also get an exception for every query that gets send to the server: "Load operation failed for query '*'. The remote server returned an error: NotFound". Substitute any query for *. Any ideas as to what I'm missing here?

TIA,
Martin.

Greg Hollywood

Posted on 5/15/2010 @ 7:39 AM

Nikhil,

I think your presentation is the best I have seen yet on Ria Services! It was very informative and helpful.

I am now trying to get the sample project to run. I have run the sql script and can connect to the database just fine. However, when i run the app, I get a "Not Found" error. I think the issue is that the Domain Service is not getting started on the server. For example, I put a breakpoint in the Application_Start in Global asax cs, but it never gets triggered. I put a breakpoint on the CreateDomainService, and it also never gets hit.

But the Global asax file is there with the appropriate code, so I don't see why it isn't being processed.

So what happens when you run the app is that it shows for a second, and then errors out on the ShowBooksOfTheDay which closes the screen. This is why several people above have noted that the app seems to run for a moment and then blank out.

Any assistance on this would be appreciated, as I am trying to implement the same structure as you have on your application. I know this is just a sample app for a presentation, but like Brad A's sample app, they seem to take on a life of their own!

Greg

Gaurav Bhasin

Posted on 8/12/2010 @ 12:53 PM

Hello Nikhil,

We have been working on researching RIA services for our new development initiative. Definetly found the book club application to be very useful. I was wondering how to load child entities along with the parent. For example using the book club application entity model, how would I load a Member and his respective books in one call from the client. I noticed on the client data context you can't use Include for the EntityQuery on the domainservice I used the "Include" but noticed the child entity wasn't pulled down to the client. I wouldn't want to make multiple calls to retrieve a parent and the child entities.

Thanks,
Gaurav Bhasin

Roy Lou

Posted on 9/30/2010 @ 2:28 PM

Hi Nikhil,
Our team started developing part of our existing website using Silverlight4 and we found your articles and video extremely helpful. We are glad to find your BookClub sample code [http://www.nikhilk.net/Content/Presentations/MIX10/BookClub.zip] and we are anxious to load it up. However when we try to open it from VS2010, we encountered the following challenges, which stops us from running it:
1. The solution was built successfully. However when we press F5, a web exception occurred at [WebServices\Amazon\AmazonService.cs line 42] – “xml = webClient.DowlnoadString(searchUri);” with the following error message: :The remote server returned an error: (407) Proxy Authentication Required”.
2. We got InvalidClientTokenId when we entered the absolute Url directly in the IE browser.
3. There is another project called “BookClubOnTheGo” along with “BookClub” & “BookClub.Web” However the solution did not load it and it will generate the “The project type is not supported by this installation” error message if we manually load it. What is this project?

Advice please! Thanks!

MIX10 Talk - Slides and Code

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