Programming with .NET - General

Re: Re: Re: WCF Services with faultexception

minus34 — Wed, 15 Jul 2009 07:41:21 GMT

Your issue is caused by Silverlight not supporting Windows Authentication. Hence a WCF service for a Silverlight app can't support Window Authentication...

It'd be nice if there was some workaround for this... But I've not heard of any.

Cheers,

Hugh

Re: Re: Re: WCF Services with faultexception

davedrat — Mon, 06 Apr 2009 08:57:42 GMT

Thanks for your quick reply sladapter,

The approach you describe seems like the right one... but I'm getting stuck at the same point as you.

There is an additional difficulty though.. If I do not change anything in the Message Inspector code, or the service web.config, then Visual Studio will not even let me add the service reference to my client Silverlight app.

VS complains that "Security Settings for this service require 'Anonymous' Authentication but it is not enabled for the IIS application that hosts this service."

Any thoughts on this?

I have contacted the codeplex guys to see if they can provide some help. If a solution is found I'll post it back here....

Cheers

Re: Re: WCF Services with faultexception

sladapter — Fri, 03 Apr 2009 15:19:40 GMT

Davedrat,

Sorry I have never done this. I'm not sure you need to change anything in MessageInspector code;

You might just need to add the Security to the binding when you create BasicHttpMessageInspectorBinding. However, I have not figure out how to specify the transport in the code.

            EndpointAddress address = new EndpointAddress(new Uri(Application.Current.Host.Source, "../Service.svc"));
            BasicHttpMessageInspectorBinding binding = new BasicHttpMessageInspectorBinding(new SilverlightFaultMessageInspector());
            binding.Security.Mode = BasicHttpSecurityMode.TransportCredentialOnly;
            // How to set the Transport here?
// binding.Security.Transport.ClientCredentialType = HttpClientCredentialType.Windows; This line won't work in Silverlight.

            ServiceClient proxy = new ServiceClient(binding, address);

            proxy.DoWorkCompleted += new System.EventHandler<System.ComponentModel.AsyncCompletedEventArgs>(proxy_DoWorkCompleted);
            proxy.DoWorkAsync();

You might want to ask this question in the codeplex site where you download the sample code and see if the creator of this solution can provide an answer.

Re: Re: WCF Services with faultexception

davedrat — Fri, 03 Apr 2009 13:47:51 GMT

Hi SLadapter,

Thanks for this link, I have implemented the code and it works well. I have one problem though...

It will only work when I have anonymous access permitted on the site which hosts the WCF Service.

For other reasons it is essential that my site has anonymous access disabled.

I assume that I have to change the BasicHttpMessageInspectorBinding to implement the equivalent of this:

</security>

But I am unclear how I would actually go about doing this in the context of the MessageInspector solution.

Any help would be gratefully received.

Cheers

Re: WCF Services with faultexception

baskarangr — Wed, 18 Mar 2009 11:19:45 GMT

Thank you!!! this link is helpful.

Re: WCF Services with faultexception

sladapter — Wed, 28 Jan 2009 19:01:49 GMT

surielb,

Thanks for the article.

Here is another similar solution from Microsoft Web Service team which basically has the same concept, but the code they provided is even more straightforward and simpler without having to change much of the current code. All you need to do to create BasicHttpMessageInspectorBinding instead of BasicHttpBinding and pass it to the Service constructor. Then the e.Error should return you all the exceptions thrown from the Service end.

See discussion in this blog: http://blogs.msdn.com/silverlightws/

You can download the Silverlight Fault Handle sample code from here:

http://code.msdn.microsoft.com/Project/Download/FileDownload.aspx?ProjectName=silverlightws&DownloadId=3473

Re: WCF Services with faultexception

surielb — Fri, 23 Jan 2009 10:23:28 GMT

I have put together an article on Code project explaining in detail a re-usable set of classes to allow Service Exception handling in Silverlight.

The code wrapps itself around the service calls and adds extra info to the response message if an exception is handled.

This solution works for all scenarios including methods that return primitives or void, and keeps the compatibility with the standard WCF Fault handling.

The article can be found at Catch and Handle WCF Service Exceptions in Silverlight

Re: Re: WCF Services with faultexception

sravoux — Mon, 22 Sep 2008 08:07:38 GMT

In order to keep the same signatures on my WCF services, I've done something like what you said (with a GetLastError() Method) :

http://silverlight.net/forums/p/19875/94861.aspx#94861

Thanks

Re: Re: WCF Services with faultexception

littlesteps — Mon, 08 Sep 2008 09:01:44 GMT

Instead of "out params" approach, I prefer to manage "Status".

Status management is a specific service dedicated to error handling with "strong-typed" errors (like non-generic FaultException).

Typically, when a method from a service returns "false", the client has to call a service like "GetLastStatus" that enables him to retrieve error details from the last call.

I design several DataContracts for different kind of Status. Basically: KernelErrorStatus, BusinessErrorStatus, and so on.

Of course this kind of approach depends on service implementation (single / per call / per session mode and multi-threading or not), and has to be designed correctly to fit well.

But I think it helps to get nice architecture for error handling and prevents developpers to "pollute" or "complicate" method signatures in the service contracts.

Hope this helps,

Re: Re: WCF Services with faultexception

jordanhammond — Mon, 01 Sep 2008 08:29:45 GMT

agreed. I use the out parameter method as it's easier than adding a property if you have a lot of DataContracts. Also hoping the FaultException is fixed in the next release so can easily strip out the out param.

Re: Re: WCF Services with faultexception

sladapter — Sun, 31 Aug 2008 14:55:23 GMT

If you do no catch the Exception thrown in your Service code, you will get 404 error. But if you catch the final exception before your Service code return, wrap that error in ResultData back or you can use Out Parameter to return the error, you should get a meaningful error instead of 404 error.

Re: Re: WCF Services with faultexception

Aaro — Sun, 31 Aug 2008 03:08:59 GMT

A Silverlight business app would need it's state managed on the server. And it's probably no coincidence that the state machine workflow service seems like it could be ideal for this. This could be a lot more elegant than the old ASP.Net session state.

However the current ReceiveActivity seems to be designed for SOAP features. So when a method is called of the wrong state all I get back is the 404 errors.

Does anyone know of a work around for this? And this seems pretty obvious way to make Silverlight apps so one of the gurus in the blogsphere must be working on a decent demo...? (that Calculator sample is pretty lame).

I can return errors within my functions using a property in a DataContract but I don't know how to override the workflow services when it throws a fault exception. I'm in process of learning how to use it so there are big gaps in my knowledge of it.

Re: WCF Services with faultexception

doolittle — Thu, 07 Aug 2008 18:20:30 GMT

Looks like you are already doing what we ultimatly would like to be doing :).
At least the part where you send the info with information on what the client is actually allowed to do with it.

You might have noticed my thread http://silverlight.net/forums/t/22022.aspx.
I'm really interested if for your, pretty big it seems, project you used any existing framework.
If not what kind of structure are you using.
I'm not asking for any code, but is it based on some guidelines?
Did you find those somewhere??
Would be very interested in that...

Re: WCF Services with faultexception

sladapter — Thu, 07 Aug 2008 16:05:37 GMT

Yes, actually I bring back meta data and real data. The meta data is for describing each field of an object such as field data type, if it's required, if it's editable, the Max field length, security right and access right check id, data format, display control type and edit control type etc. With all those information we basically can automate control building process.

Most security check are done in the Business tier so the data I bring back is for the current user only. If the user does not have certain right for certain field, the data returned won't even contains that information.

Our data requirements is not simple at all, it need to be very dynamic. Each user can select different columns (within their right) to show their data. They can change this selection dynamically. Because the nature of our data requirement is so dynamic, generic way (using DataSet rather than define each DataObject) is a better way for us. It requires a lot of thinking before hand and it's not that straight forward either. But once the structure is there, adding more objects and pages are simple and easy.

Re: WCF Services with faultexception

jordanhammond — Thu, 07 Aug 2008 15:38:47 GMT

sladapter, it would be nice to have such simple data requirements.

Do you not need to bring back combined information? such as details of a client with lists of things they're allowed to do?