Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

eKyNoX23 — Fri, 17 Jul 2009 10:21:39 GMT

Hello,

i am very interested to make a webiste where silverlight plugin take all the browser size but if my website start to have many pictures, files ... in it, is there any way to do not have to load all the website at startup included inside one .xap file ?

Thanks for answer.

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Martin — Fri, 17 Jul 2009 11:59:20 GMT

Hi Brad,

Excellent stuff - thanks.

Can you confirm whether DomainServices work with Table-per-Type "inheritance" classes?

For example, say you have an EntityFramework model with a Person entity (PersonId, FirstName, LastName, DateOfBirth) and a derived Contact entity (PersonId, Email, PhoneNumber).

Should I expect a ContactDomainService class to "just work"? If not, what is the best practice with the current version of RIA Services/Entity Framework?

Thanks,

Martin

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Zoran — Fri, 17 Jul 2009 14:01:51 GMT

These examples are really excellent way of getting into RIA. Thank you Brad.

I know this is not "Make a wish" type of blog but :)

What would be nice to see is more complex scenario when your app is vertically segmented into several DomainServices. (I.e. "Contact Management", "Product Management", ... but all toghether is wired into singe application). I am personally having problems to understand how conceptually RIA is supposed to be used in such situations. Key thing are I guess transactions which needs to span across more than one DomainService.

Thanks,

Zoran

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

John Schroedl — Fri, 17 Jul 2009 16:05:03 GMT

I think it would be enlightening if you could post about the approach you would take if those ErrorMessage values needed to be localized according to the client's locale.

John

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Dave — Sat, 18 Jul 2009 00:16:48 GMT

Hi Brad,

Thanks so much for this latest set of articles. They have been extremely helpful.

In regards to your DTO approach, we were actually going this way, but found that there are some issues with this approach when you try to shape or filter the data on the client side. For example, if you try and run a query operation from Silverlight to only return SuperEmployees that have a name starting with the letter A, you would do something similar to:

var query = context.GetSumperEmployeeQuery().Where(emp=>emp.Name.StartsWith("A");

context.Load(query);

This operation will throw a LINQ To Entities exception, but maybe I am just doing something wrong on my side, so I would be interested to know if you tried this. We also ran into the same problem when trying to load up these DTO objects with their associations.

Anyways, just thought I would point that out.

Thanks again Brad.

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

BradA — Mon, 20 Jul 2009 00:46:57 GMT

Dave – hmm… Not sure why you are hitting this, but client side queries like that should work… this is exactly how the filtering works in this example.. can you post a repro on the forums so we can take a look at it?

..brad

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

BradA — Mon, 20 Jul 2009 05:34:52 GMT

> Can you confirm whether DomainServices work with Table-per-Type "inheritance" classes?

Nope -- inhertance is on the feature list, but it is not currently implemented.. Do you think tihs is a critical scenario?

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Martin — Mon, 20 Jul 2009 11:37:02 GMT

> Can you confirm whether DomainServices work with Table-per-Type "inheritance" classes?

> Nope -- inhertance is on the feature list, but it is not currently implemented.. Do you think tihs is a critical scenario?

Well, I need to deal with Table-per-type "inheritance" classes in my current project. If it is not currently implemented, can you describe:

a) What I should expect to happen if I try it (e.g. what goes "wrong")

b) How I can best deal with the scenario, e.g. can I get some of the benefits of RIA Services if I override some of the "out-of-the-box" behaviour (DomainService.Submit, for example)?

Thanks,

Martin

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Robert Kozak — Tue, 21 Jul 2009 21:58:50 GMT

Brad,

The SuperEmployeeDTO is still an Entity. How does this really work as a DTO which should be smaller and lightweight?

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

BradA — Wed, 22 Jul 2009 00:11:51 GMT

In what what is it an entity? you mean on the client or server?

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Robert Kozak — Wed, 22 Jul 2009 02:25:09 GMT

Both. SuperEmployeeDTO on both the Server and the generaqted code on the Client still derive from Entity.

I was hoping for a better separation between Models that the application needs to use and the model that RIA Services needs for the database.

Basically, continuing with your example, I would love to have an ISuperEmployeeDTO and a POCO implementation of ISuperEmployeeDTO. Is this possible?

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Robert Kozak — Wed, 22 Jul 2009 02:35:52 GMT

Correction. SuperEmployeeDTO on the Server is just an object but on the client it is an Entity type.

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

BradA — Wed, 22 Jul 2009 05:36:09 GMT

Robert -- that is right, the server is POCO, the client does derive from a base class that has helpers to deal with data binding and data validation, etc.. My thinking was that this was boilerplate enough to not be a problem.. If you want PURE POCO on the client you can use use the Astoria REST head on DomainService, but you'd lose some of the validation and binding benefits.

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Robert Kozak — Wed, 22 Jul 2009 17:35:13 GMT

Thanks, my devs are complaining that it seems like more work and maintenance to create a DTO (especially since we renegineered the backend database to match more closely the classes used in the application) if they look like the original DALs. If RIA services could surface interfaces it would be an easier "sell" to develop DTO classes.

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Andy Schroeder — Wed, 22 Jul 2009 17:55:45 GMT

I may be totally wrong about how the Query Methods are working here, but would using the DTO object like this have an effect on the way linq queries get translated to sql statements?

When you use the LinqToEntitiesDomainService, the client passes linq queries down to the service, including "where clauses" added by your DomainDataSource.FilterDescriptors. These linq queries get combined with any on the service and ultimatly generate sql such that all the filtering is happening on the database. (i.e. in your example the "Origin StarsWith" filter from the UI would ultimatly result in a where clause in the database)

However, once you stop returning EF entities from the Domain service, then only the linq over EF context gets translated to a sql statement, and the linq passed from the client is applied to the result as an in-memory filter. (still filtered on the web server, but not at the database level)

Am I understanding correctly?

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

BradA — Fri, 24 Jul 2009 21:05:04 GMT

Andy Schroeder - Even in this case, the query executes on the DB directly... basically the Linq provider here is smart enough to do the right things with projections. Let me know if you are seeing something different happen.

..brad

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Andy Schroeder — Sat, 25 Jul 2009 00:47:34 GMT

Wow, I'm supprised the provider is able to handle that. The projection is the key that i missed here.

I planned the transition from linq object to DTO outside the linq query syntax (like a helper mapping function to translate to a DTO, instead of projecting it in the linq query) then that would have prevented the provider from combining the linq queries.

I guess my thought process is that if you inject DTO's in there you need to be careful not to make a change that prevents the provider from helping you out and moving the filtering all the way to the db.

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

pianomanjh — Wed, 29 Jul 2009 02:08:55 GMT

Please include inheritance in the next release. I definitely believe this is critical. Supporting the concept of super/subtypes in a database encourages good design. I currently have a project that would use RIA Services, save for this key deal-breaking limitation.

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Stefan Olson — Wed, 29 Jul 2009 04:25:53 GMT

Brad,

I absolutely think that inheritance is CRITICAL. In the project I'm currently working on I have managed to avoid inheritance up till now, but today I have a particular scenario where I need inheritance.

.net ria services as it currently stands will try and flatten my inherited classes. The problem with this is that it requires a large amount of code replication. For example I've got a base Favourite class and derived FavouriteItem and FavouriteUser etc.... If I had inheritance I would only have to set up the shared object properties which sit in the base class once (in the constructor or whatever).

Given that I have 4 derived classes I now have to have the same code duplicated 4 times!

In this particular situation I may be able to work around that by doing the object setup on the server. However, my next .net ria services project which uses a fairly complex multilevel inherited entity framework database structure will not have the same flexibility. It is absolutely crucial that I can address objects polymorphicly on the client - otherwise the project won't be able to work.

...Stefan

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Rob Harwood — Sun, 09 Aug 2009 22:38:15 GMT

I second inheritance being critial.. Inheritance (especially table-per-type) seems to have been heavily pushed with the introduction of EF but then got sort of forgotten about, for example it is _very_ easy to have EF spew some god awful SQL when querying base types, ADO.NET Data Services doesn't support it properly (no OfType operator) and now RIA services, which by the way is a bloody cool technology, doesn't support it at all and the flimsy flattening support doesn't generate buildable code from my entity model which has locked me out entirely. =(

Flattening is problematic because it means rewriting validation/logic for base properties for every type of entity which is surfaced with RIA Services, plus its nice to be able to write UI which can take a base type as a model and present the shared properties, which would not be possible with the clientside classes currently generated by RIA services.

The whole point of having EF Support inheritance was to allow developers to surface models that are more natural to work with, which are abstracted from the data source. If RIA services just reflattens the structure it is directly negating one of the core principals of using EF.

I really hope that VS2010 and it's related technologies will begin to sort the inheritance support nightmare out!

re: Business Apps Example for Silverlight 3 RTM and .NET RIA Services July Update: Part 6: Data Transfer Objects (DTOs)

Yanal — Thu, 01 Oct 2009 16:41:36 GMT

When you insert a new record using POCO, how would you get back the ID, if the ID column in database was autogenerated.