Using Autofac for DI into WCF service hosted in ASP.NET application - asp.net

Question

I'm having trouble injecting services dependencies into my WCF service using Autofac 1.4.5. I've read and followed the Autofac wiki page on WcfIntegration but my debugging shows me that my WCF service is created by the System.ServiceModel.Dispatcher.InstanceBehavior.GetInstance() method and not by the AutofacWebServiceHostFactory. What am I doing wrong?
I've set up my ajax.svc file to look like the one in the example for use with WebHttpBinding:
<%# ServiceHost Language="C#" Debug="true"
Service="Generic.Frontend.Web.Ajax, Generic.Frontend.Web"
Factory="Autofac.Integration.Wcf.AutofacWebServiceHostFactory,
Autofac.Integration.Wcf" %>
My WCF service class Ajax is defined like this:
namespace Generic.Frontend.Web
{
[ServiceContract]
[AspNetCompatibilityRequirements(
RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class Ajax
{
public MapWebService MapWebService { get; set;}
public Ajax() {
// this constructor is being called
}
public Ajax(MapWebService mapWebService)
{
// this constructor should be called
MapWebService = mapWebService;
}
[WebGet(ResponseFormat = WebMessageFormat.Json)]
[OperationContract(Name = "mapchange")]
public MapChangeResult ProcessMapChange(string args)
{
// use the injected service here
var result = MapWebService.ProcessMapChange(args);
return result;
}
}
}
Now I've used the wiring up in the Global.asax.cs as shown in the wiki mentioned above:
var builder = new ContainerBuilder();
builder.RegisterModule(new AutofacModuleWebservice());
var container = builder.Build();
AutofacServiceHostFactory.Container = container;
with
class AutofacModuleWebservice : Module
{
protected override void Load(ContainerBuilder builder)
{
builder.Register<Ajax>();
builder.Register<MapWebService>().ContainerScoped();
}
}
In my web.config I have
<services>
<service name="Generic.Frontend.Web.Ajax">
<endpoint address="http://mysite.com/ajax.svc/" binding="webHttpBinding"
contract="Generic.Frontend.Web.Ajax" />
</service>
</services>
.
The service already works fine but I can't get the Autofac bits (read: creation/injection) to work. Any ideas?
Edit:
Removing the default constructor unfortunately leads to the following exception:
System.InvalidOperationException:
The service type provided could not be loaded as a service because it does not
have a default (parameter-less) constructor. To fix the problem, add a default
constructor to the type, or pass an instance of the type to the host.
Cheers, Oliver

Answer 1

Is your service setup with InstanceContextMode.Single? If it is then wcf will create your service using the default constructor. To get around this change your instance context mode and let autofac manage the lifetime of your service.

Answer 2

Try deleting the default Ajax constructor and modifying your constructor to this. If it gets run with mapWebService == null that would indicate a resolution problem.
public Ajax(MapWebService mapWebService = null)
{
// this constructor should be called
MapWebService = mapWebService;
}

Answer 3

I just got the same System.InvalidOperationException and solved it by changing the ServiceBehavior InstanceContextMode of the implementation from InstanceContextMode.PerCall to InstanceContextMode.PerSession, perhaps your AutoFac lifetime scope is out of sync with your web service implementation?
For testing AutoFac service creation I recommend creating a unit test and directly resolving them as this will highlight any issues and give more meaningful exception messages. For services with a request lifetime scope create a test aspx page and again resolve them directly.

Answer 4

I had the same problem and came across this question while searching for an answer.
In my case, using property injection worked, and the code in the question already has a property that can be used:
namespace Generic.Frontend.Web
{
[ServiceContract]
[AspNetCompatibilityRequirements(
RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class Ajax
{
// inject the dependency here
public MapWebService MapWebService { get; set;}
[WebGet(ResponseFormat = WebMessageFormat.Json)]
[OperationContract(Name = "mapchange")]
public MapChangeResult ProcessMapChange(string args)
{
// use the injected service here
var result = MapWebService.ProcessMapChange(args);
return result;
}
}
}
and register to use property injection (sample code from the wiki and syntax has changed as this is now using version 2.5.2.830):
builder.RegisterType<Ajax>().PropertiesAutowired();

Answer 5

Following the instructions solved it for me:
code.google.com/p/autofac/wiki/… I simply do : builder.RegisterType();
and I've followed their instuructions for changing the .svc file.
When you look at your .svc file you do not get any hints about something being wrong there btw?
You host it throu the iis and do not utilize WAS, I do not see your code for overriding global.asax.cs
Add the global file to your solution and there you implement:
protected void Application_Start(object sender, EventArgs e)
{
// build and set container in application start
IContainer container = AutofacContainerBuilder.BuildContainer();
AutofacHostFactory.Container = container;
}
AutofacContainerBuilder is my container builder.