How to properly handle WCF faults with Silverlight? - wcf

Question

No matter how hard I try I cannot seem to be able to handle WCF faults in Silverlight.
In fact the error seems to never leave the server !
E.g. when I debug it, it stops on the line where I throw the FaultException saying it was not handled:
[SilverlightFaultBehavior]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class StoreService : IStoreContract
{
public System.Collections.Generic.List<string> GetStoreDesignNames()
{
try
{
StoreDataContext swdc = new StoreDataContext();
var query = from storeDesign in swdc.StoreDesignDBs select storeDesign.Name;
return query.ToList();
}
catch (System.Data.SqlClient.SqlException sqlExcept)
{
throw new FaultException<SqlFault>(new SqlFault() { Message = sqlExcept.Message });
}
}
}
The class that implements this method derives from a contract interface:
[ServiceContract(Namespace = "Store")]
public interface IStoreContract
{
/// <summary>
/// Obtain the list of store design names.
/// </summary>
[OperationContract,
FaultContract(typeof(SqlFault))]
List<String> GetStoreDesignNames();
}
And the SqlFault class is defined like this:
public class SqlFault
{
public String Message { get; set; }
}
On the client side I handle the error as follow:
// swc is the client
swc.GetStoreDesignNamesCompleted += new EventHandler<ServiceReference.GetStoreDesignNamesCompletedEventArgs>((obj, evt) =>
{
if (evt.Error == null)
{
// In case of success
MessageBox.Show(evt.Result.First());
}
else if (evt.Error is FaultException<ServiceReference.SqlFault>)
{
FaultException<ServiceReference.SqlFault> fault = evt.Error as FaultException<ServiceReference.SqlFault>;
Dispatcher.BeginInvoke(() =>
{
ErrorWindow ew = new ErrorWindow(fault.Detail.Message, "No details");
ew.Show();
});
}
});
swc.GetStoreDesignNamesAsync();
I have tried to put the [SilverlightFaultBehavior] attribute on the interface, to no avail. Even if I do without the interface I still have this error.
I have also tried to use a behavior extension in the web.config as described here but I get a warning saying the extension is not valid.
How does one go about properly handling WCF fault in Siverlight ?
Thanks in advance.

Answer 1

I haven't used WCF (been using WCF RIA Services) but I did come across this article a while ago.
Getting something better than “Server not found.” from WCF in Silverlight

Answer 2

After battling with this for hours I finally hacked something together that works.
This is really a horrible hack and I would have much preferred to use BehaviorExtension for this task. The trick is to set manually the HTTP status code in the body of the WCF method like so:
public System.Collections.Generic.List<string> GetStoreDesignNames()
{
try
{
StoreDataContext swdc = new StoreDataContext();
var query = from storeDesign in swdc.StoreDesignDBs select storeDesign.Name;
return query.ToList();
}
catch (System.Data.SqlClient.SqlException sqlExcept)
{
System.ServiceModel.Web.WebOperationContext ctx = System.ServiceModel.Web.WebOperationContext.Current;
ctx.OutgoingResponse.StatusCode = System.Net.HttpStatusCode.OK;
throw new FaultException<SqlFault>(new SqlFault() { Message = sqlExcept.Message });
}
}
The error message then correctly displays on the client side.
If anybody has a better solution than this I'd like to hear it.