At the moment it seems that a RIA Domain Services class can not return a sinlge custom type.
There are parts of my app that needs just that, so think the only way to get that is to call back to a simple silverlight-enabled WCF Service, which i beleive will not have a problem returning a custom type. I don't see where the Silverlight client app has any sort of reference to the Ria Services. How do I set up both a Ria services and WCF service on the silverlight client. Will the WCF service be "aware" of the authenication already in place with the RIA services?
This is one of my biggest bugbears of RIA Services :). The good thing is that they are in the process of enabling complex types to be returned from invoke methods (according to the user voice site for RIA Services). However, that won't help you now :).
The best way to implement your requirement to return complex objects is indeed to set up a standard WCF Service to return complex types when required. You do so in the normal way that you would expose a WCF in any web project. You then consume it in your Silverlight application in much the same way you would a WCF Service in any other type of project (by adding it as a service reference). The main difference when consuming it (compared to other types of projects) is that Silverlight only supports asynchronous calls. One difference to be aware of from RIA Services is that whereas RIA Services automatically determines the URI of the domain services (based upon where the XAP file originated from), you will need to handle that aspect yourself (very important when you try to deploy your application :). Do this either by setting the URI in the app.config file, or use the method I use in the code accompanying this article here: http://www.silverlightshow.net/items/Building-a-Framework-for-Silverlight-Line-Of-Business-Applications.aspx.
In regards to your final question, yes, RIA Services uses standard ASP.NET authentication, so the cookie that it uses to maintain your authentication status is also used by any WCF Services in the same project. I talk a bit about security with WCF Services in this article if you want more information: http://www.silverlightshow.net/items/Building-a-Silverlight-Line-Of-Business-Application-Part-3.aspx.
Hope this helps...
Chris
Related
I am going to develop the 3 tier application using Silverlight + WCF + ORM
Now my question is if I use ORM at database layer then how can I expose the classes at Presentation, Business layer to do Client-Side validation ?
If you used WCF RIA services instead of plain Silverlight WCF, you can attribute the properties of your data objects (in the associated metadata classes RIA creates for you).
This allows you to add basic validation rules, or even custom ones, that runs on both the server and client.
Using WCF RIA Services via a library is the preferred way to organise projects so try this link:
Walkthrough: Creating a RIA Services Class Library
Also:
Using WCF RIA Services
Creating Rich Business Applications using Silverlight 4 and WCF RIA Services
Various Channel 9 Videos
Is is generally a bad idea to expose your business entities directly to the frontend. Not only is what fits your backend layer rarely a good fit for your frontend but you also run the risk of exposing security critical information to the client - which should never be trusted.
An approach that generally worked well for us is developing the Silverlight Frontend using the MVVM pattern and have your WCF Service Layer return DTOs that can be more or less directly mapped to the data requirements of a ViewModel. This also satifies one of the most important rules when developing intranet/internet client server applications and that is to keep roundtrips to a mimimum because a DTO tailored to the needs of a particular viewmodel can include all the relevant information at once.
I have a WCF service (using HTTP binding) that our WinForm and WFP apps can use with no problem. We have a Silverlight 4 developer who is saying he's not able to use the WCF service because it needs to be "reconfigured" for Silverlight use. I don't know if this is true or not, because I don't know anything about Silverlight.
So, my question is this. Should a WCF service, that uses HTTP binding, that is successfully being used by our WinForms and WPF applications, also be able to be consumed by Silverlight apps, without modifying or reconfiguring the WCF service?
Silverlight 4 supports the following bindings:
BasicHttpBinding
PollingDuplexHttpBinding
CustomBinding (with a subset of binding elements)
Silverlight and WCF Feature Comparison:
There are several ways to use the WCF
client stack to access a service.
It is used when invoking services
through automatically generated
proxies, as described in How to:
Access a Service from Silverlight. The
proxy must be generated in this
procedure by using the Add Service
Reference tool in Visual Studio 2010
for the Silverlight project.
Caution:
Proxies generated by using the WCF
Svcutil.exe tool will not work in
Silverlight 4. Use the SLsvcutil.exe
tool instead. For more information
about using this Silverlight tool, see
Using SLsvcUtil.exe to Access a
Service.
If you already have a Windows
Communication Foundation (WCF) service
contract definition, you can use the
generic ChannelFactory class without
having to generate a proxy. This might
be the case, for example, if your
client is sharing service definition
code with the project on the server.
In this case you could, for example,
define a service contract interface
IStockQuoteService and then use the
same IStockQuoteService code in both
the server and Silverlight projects.
This would involve using a
ChannelFactory.
This advanced technique is
demonstrated in How to: Call
Operations Asynchronously Using a
Channel Factory and in the Silverlight
4 context with Building and Accessing
Duplex Services. For more information
about defining and using service
contracts, see Designing Service
Contracts.
I'd like my WP7 to be able to talk to a service on my local computer. For various reasons it would be more convenient if this service was hosted in a custom host, i.e. an app running locally. However, if I understand correctly "Silverlight-enabled WCF service" need asp.net compatibility, therefore must be hosted in IIS, is this correct?
If so, is there anyway to work round this and get a "Silverlight-enabled WCF service" running in a custom host?
The Silverlight-enabled WCF Service is just a simplified item template from a regular WCF service. It was originally added because the default binding for WCF services wasn't supported in Silverlight, and caused a lot of angst for new Silverlight developers. You should be able to use the regular WCF item in a regular project (e.g. console app) and you'll just have to adjust the bindings.
(Also of note is that the Silverlight-enabled WCF template uses a single code file instead of separating out the service interface from the class implementation.)
I have my silverlight calling my WCF service and its working great. This is a WCF (not ria) service that basically returns enitites or collection of entities.
I really don't have control over it to add additional items just for silverlight for example.
So i was thinking but maybe its bad performance or desgin..
But to have a local WCF Service hosted with the Asp.net website that hosts silverlight.. ANd i can use this wcf service for business logic that doesn't need to return entities. For example so silverlight can call to the server and then the server can do something with PURE .net.
Of course i still will need my silverlight to talk to my External WCF service that returns entities etc..
What would be the best way to implement this, if at all..
Silverlight calls local WCF service and "IF REQUIRED" local wcf service calls external WCF Service (which returns entities etc) and everything is returned back down the chain.
or Silverlight calls to local WCF service or to external WCF service depending on what is required.
There is a 3rd option but i am thinking aloud and maybe it wouldn't fit... But to have RIA services so silverlight could call this .... but again I CANNOT get rid of or have control over my other wcf service... So silverlight would need to call both OR ria services could call the wcf service ... But this is where i have a doubt... because RIA services normally return IQUERYABLE for example... My wcf service returns ILIST for example so if ria services called to my wcf service it would receive back an ILIST .. hence the [QUERY] attribute in ria services require me to return IQUERYABLE but it isn't possible because i am already in an ILIST.
I would really appreciate some feedback to weather i am completely missing the point or infact its a good idea.
The fact remains that silverlight sometimes needs to do standard stuff on the server but has nothing to do with dataaccess or entities... i have no control over the external wcf service so i can't just insert a new method specifically for silverlight when its needed..
Anybody use a similar system, PROS / CONS??
Thanks in advance
I think your application should use only Ria Services and then Ria service should connect to the external service. Then all logic is on the server and your SL app has simple model of using services. You can think about is as all business logic is on the server.
What about returning IQueryable you always can "convert" list to IQueryable using linq, but I think you can return list from RIA Service - it shoudn't be a problem.
Before reading, please know I've read all the other posts about the differences between vanilla WCF, WCF Data Services and RIA Services. My question is specifically about why RIA Services is being considered as a special kind of data source specifically for Silverlight when it seems to make more sense to just have it do one job: serve as a business logic layer behind a REST interface.
It looks like with the release of VS2010, RIA Services has solidified its stance as a business logic layer that sits behind a REST data access service - this seems to be confirmed by the new "Expose OData Endpoint" option on the Domain Service Class template in Visual Studio, which as far as I can tell essentially does for your RIA Service exactly what WCFDS does for an arbitrary data source (you could do this before, I believe, but the addition of this checkbox makes it clear that a RIA Service can be viewed as a layer containing business logic used to enhance a REST data endpoint and/or constraint it to a given set of queries, and not necessarily an endpoint in and of itself).
So, if I've got a RIA service with business logic, exposed via OData, I can add a reference to the OData service from a WCF client app. On the client, I get a DataServiceContext derivative that lets me do unit-of-work style work on the client. I can do the same thing from a Silverlight app and get what appears to be the same thing - a DataServiceContext derivative.
If I instead use a "RIA Service Link" in my Silverlight app to directly tie the app to the RIA service instead of adding a service reference, I get code generated by Visual Studio that appears to support pretty much the same patterns of work, but using a different style of API.
That being the case:
What are the advantages of a "RIA Services link," where a Silverlight app is tied directly to a RIA Service, as opposed to just adding a service ref to an OData endpoint that can be consumed by any kind of client without incurring tight coupling? I'm told that the magic of RIA is in the code generation, so I guess I'm trying to understand how the RIA code generation differs so much from "add service reference" code generation.
If there are advantages, why are these advantages made available specifically to Silverlight and not WCF client apps? Selling RIA services purely as a layer behind an OData endpoint seems like it would help standardize and push OData even further in terms of becoming a universal type of endpoint for any sort of client – “consume from ASP, consume from Silverlight, consume from WCF… you get virtually the same experience and it’s a great one.” Instead, we have Silverlight tied directly to RIA with a special set of functionality, and all other clients using the open protocol.
RIA services is not intended as "Domain logic behind oData" to the contrary and quite the opposite. The intention of RIA services is to abstract away the mechanics of web based data access to enable Rapid Application Development in Silverlight. Think of RIA
Services as to WCF as VB is to C++.
The key benefits of RIA Services are:
Transparent Data Access - there's no fiddling with svc files etc. You create an entity framework model, wrap it in a domain service and you're done. More importantly changes are propagated automagically. The developer doesn't have recreate the Service reference every time the model or a query changes, code gen does it for you.
Authentication framework out the box - It's there when you create a business app, it's a template in VS, a way to integrate with existing ASP.NET auth without having to do any heavy lifting.
Data Source Templates and Validation = Probably one of the most overlooked features but yet one of the most important. Have you opened the "data sources" window? RIA services creates User configurable DataContext bound Master/detail controls that support server side validation annotations. A functional data bound app is a drag and drop away. Consider the value of that to someone who is more Design/Blend focused.
In short RIA services is built for a developer to be able to go from an edmx data model to a secure functional Silverlight up in a matter of hours. It's awesome stuff when used in context.
As a note, I've done quite a bit of research on RIA Services and Data Services and they fulfill different needs. We use RIA Services for all our desktop replacement apps, but we use Data Services for SaaS.
I don't think you're far off with the long term intention of RIA services though. I think we'll see oData and RIA services get a lot closer in future versions.
The OData endpoint exposed by WCF RIA Services does not support query operations and returns data as-is. That means no benefit from IQueryable, sorting, parameters, etc. It will simply expose your methods; end of story. There is rumor that this will change in the next release however. However, what RIA Services provides from the standpoint of IQueryable on service calls, automatic propagation of business rules from the middle tier to the UI, and INotifyDataErrorInfo for flowing validation errors to the Silverlight client is outstanding should you choose to leverage them.