DataServices - Mike Taulty's Blog

A big thanks to all the people who came along to my session at SQLBits today on ADO.NET Data Services and also to the organisers and community around SQLBits that made the event happen in the first place. I was there for most of the afternoon and it seemed like a fantastic event to me in a cool venue. As promised, my slides from the session are here for download – you’ll perhaps notice that there are a few additional (hidden) slides in the slide-deck that I didn’t use in this talk as I collapsed this talk down from an earlier talk and updated it to reflect the RTM version of Data Services and also the various CTPs/Previews that are currently kicking around. So…you get a little more than I actually used at the conference. Enjoy :-)

I produced a new set of short videos around ADO.NET Data Services and dropped them on to Channel 9. You can find them here; http://channel9.msdn.com/tags/UK and that list will grow as time goes in ( specifically, it'll grow if I can get the publishing system to publish my next 4 videos for me as it's not playing ball at the time of writing :-) ).

Someone mailed me to ask whether I had a video on how to put together Silverlight and ADO.NET Data Services. I don't at the time of writing and I've also got a cold right now ( thank you, Microsoft Manchester office :-) ) so I thought I'd write something rather than record it. Let's run through a step-by-step thing. Visual Studio 2008 - File->New->Web Site. I'm going for the filesystem and C# as below; Now, to make it easy to work with ADO.NET Data Services, I'm going to add in an ADO.NET Entity Data Model for Northwind. That is ... Website->Add->New Item; I say "yes" to add it to my app_code folder, then select; and then I can go and add a new ADO.NET Data Service ( again via Website->Add New Item ); and then I can update my service code to read; public class Service : DataService<NorthwindEntities> { // This method is called only once to initialize service-wide policies. public static void InitializeService(IDataServiceConfiguration config) { config.SetEntitySetAccessRule( "*" , EntitySetRights...

Something that I came across today - if you're trying to surface a LINQ to SQL data source via the latest build of ADO.NET Data Services and you're running datasvcutil.exe on the metadata of the service then you might find yourself with a whole bunch of errors. Here's a sample of what I was getting this morning; error 7001: Schema specified is not valid. Errors: $metadata(0,0) : error 0005: The 'Namespace' attribute is invalid - The value '' is invalid according to its datatype ' http://schemas.microsoft.com/ado/2006/04/ edm:TNamespaceName' - The Pattern constraint failed. For me, I resolved this by just making sure that I revisited my DBML diagram for LINQ to SQL in Visual Studio and set the "Entity Namespace" property for code generation. That is, click on the white-space of the diagram; to make sure that you have the diagram rather than a particular entity set selected. Then hit F4 for the properties; and give yourself a namespace and all the errors seem to go away reasonably quickly :-)

Just like for batching, there's a great explanation of how concurrency looks in ADO.NET Data Services up here so this is just a basic example. If I take the "Hello World" style service that I built back here then it does nothing about concurrency checking because, by default, when you build an entity data model with the Entity Framework tooling all of the concurrency options are set to "off". So, if I make a request for a customer and trace it with Fiddler then I see; You can see that I'm requesting the ALFKI customer and I'm just doing it from a browser as it happens. Now, if I go and alter my entity data model a little bit to say that ( purely for instance ) I want to have concurrency checking done on the PostalCode, Country, Region, Address fields of the Customers entity type as in; Then the next time I request that entity I see an ETag header being emitted that contains the value of my concurrency token; and if I was to request lots of customers then I'd see these ETags move into the response data as in; From...

Someone asked me about this so I thought I'd share here. The question was around how you can work with database generated values and have them returned to the client after the insert. My experiment ran like this. I created a table; create table test ( id int identity primary key not null , someColumn nvarchar(30) not null ) I created a website project, added an entity model which only has the table above in it and then added an ADO.NET Data Service and exposed my entity model through it in the standard way. I then used webdatagen.exe in order to read the metadata and build client proxy code. I then used that proxy class (called demoEntities below) to write a client; demoEntities entities = new demoEntities( "http://localhost:32768/WebSite1/ServiceOne.svc" ); entities.MergeOption = MergeOption.OverwriteChanges; test newTestRecord = new test() { someColumn = "foo" }; entities.AddObject( "test" , newTestRecord); entities.SaveChanges(); Console.WriteLine( "New id is {0}" , newTestRecord.id); and that all seemed to...

Just a quick link to make this easier to find; ADO.NET Data Services Silverlight Add-On

One of the things that I briefly mentioned in this post was the idea that because Data Services sits atop of WCF you can plug in a ServiceAuthorizationManager which gets a chance to look at every request before it gets dispatched into your data service. Whilst you can write explicit interceptors that pick up CRUD operations for particular entities, you might want to just have some roles such as createRole, readRole, updateRole, deleteRole and it'd be a bit painful to have to write lots of interceptor methods to enforce this. That is, it'd be nice if Data Services had a single place where you could inject code to run before (and possibly after ) each operation but I don't think it has one in the current CTP. A ServiceAuthorizationManager implementation might help a little here though. I might do something like this to try and determine who it is that's calling my service and whether I allow them to do it based on a role; public class AuthManager : ServiceAuthorizationManager { static AuthManager() { // Probably...