@draft
Implementing IErrorHandler for WCF services is a great way to centralize error handling and logging. The implementation shown here should catch any unhandled exception that is thrown as a result of a call to one of your WCF services. Also shown in this example is how to return a custom object, and how to return JSON rather than the default XML.
Implement IErrorHandler:
using System.ServiceModel.Channels;
using System.ServiceModel.Dispatcher;
using System.Runtime.Serialization.Json;
using System.ServiceModel;
using System.ServiceModel.Web;
namespace BehaviorsAndInspectors
{
public class ErrorHandler : IErrorHandler
{
public bool HandleError(Exception ex)
{
// Log exceptions here
return true;
} // end
public void ProvideFault(Exception ex, MessageVersion version, ref Message fault)
{
// Get the outgoing response portion of the current context
var response = WebOperationContext.Current.OutgoingResponse;
// Set the default http status code
response.StatusCode = HttpStatusCode.InternalServerError;
// Add ContentType header that specifies we are using JSON
response.ContentType = new MediaTypeHeaderValue("application/json").ToString();
// Create the fault message that is returned (note the ref parameter) with BaseDataResponseContract
fault = Message.CreateMessage(
version,
string.Empty,
new CustomReturnType { ErrorMessage = "An unhandled exception occurred!" },
new DataContractJsonSerializer(typeof(BaseDataResponseContract), new List<Type> { typeof(BaseDataResponseContract) }));
if (ex.GetType() == typeof(VariousExceptionTypes))
{
// You might want to catch different types of exceptions here and process them differently
}
// Tell WCF to use JSON encoding rather than default XML
var webBodyFormatMessageProperty = new WebBodyFormatMessageProperty(WebContentFormat.Json);
fault.Properties.Add(WebBodyFormatMessageProperty.Name, webBodyFormatMessageProperty);
} // end
} // end class
} // end namespace
In this example we attach the handler to the service behavior. You could also attach this to IEndpointBehavior, IContractBehavior, or IOperationBehavior in a similar way.
Attach to Service Behaviors:
using System;
using System.Collections.ObjectModel;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.ServiceModel.Configuration;
using System.ServiceModel.Description;
using System.ServiceModel.Dispatcher;
namespace BehaviorsAndInspectors
{
public class ErrorHandlerExtension : BehaviorExtensionElement, IServiceBehavior
{
public override Type BehaviorType
{
get { return GetType(); }
}
protected override object CreateBehavior()
{
return this;
}
private IErrorHandler GetInstance()
{
return new ErrorHandler();
}
void IServiceBehavior.AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters) { } // end
void IServiceBehavior.ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
{
var errorHandlerInstance = GetInstance();
foreach (ChannelDispatcher dispatcher in serviceHostBase.ChannelDispatchers)
{
dispatcher.ErrorHandlers.Add(errorHandlerInstance);
}
}
void IServiceBehavior.Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase) { } // end
} // end class
} // end namespace
Configs in Web.config:
...
<system.serviceModel>
<services>
<service name="WebServices.MyService">
<endpoint binding="webHttpBinding" contract="WebServices.IMyService" />
</service>
</services>
<extensions>
<behaviorExtensions>
<!-- This extension if for the WCF Error Handling-->
<add name="ErrorHandlerBehavior" type="WebServices.BehaviorsAndInspectors.ErrorHandlerExtensionBehavior, WebServices, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
</behaviorExtensions>
</extensions>
<behaviors>
<serviceBehaviors>
<behavior>
<serviceMetadata httpGetEnabled="true"/>
<serviceDebug includeExceptionDetailInFaults="true"/>
<ErrorHandlerBehavior />
</behavior>
</serviceBehaviors>
</behaviors>
....
</system.serviceModel>
...
Here are a few links that may be helpful on this topic:
https://msdn.microsoft.com/en-us/library/system.servicemodel.dispatcher.ierrorhandler(v=vs.100).aspx
Other Examples: