Hosting WorkflowService (WorkflowRuntime) in IIS using WCF

Question

Hi,

I'd like to host some kind workflow service (using Windows Workflow Foundation) within the IIS. Therefore I have configured a service file (.svc) and an appropriate web.config file.

When the service starts (managed by IIS?) it should load the WorkflowRuntime instance. Therefore I've created a class implementing the IExtension<ServiceHostBase> interface holding that instance.
Because my application is not directly responsible for creating the ServiceHost (-> IIS) - how can I add this extension to the service host? Is it possible to configure this via the web.config file (<extensions>-Element)? Or do I have to write such a class inheriting from ServiceHostFactoryBase and configuring the service file?

Thank you!

Answer 1

Did you ever found the solution for this ?

Answer 2

That's a WCF question, not a WF question .

You can either attach the IExtension using a custom ServiceHostFactory, or inject it using a IServiceBehavior. The latter approach can be implemented using an attribute that you can attach to your service implementation:

[WorkflowBehavior]
public class MyWorkflowEnabledService : IMyWorkflowEnabledService
{
   //...
}
  

There's also a new whitepaper on integrating WCF and WF.

 

Answer 3

What I am doing now is the following: when I need the workflow runtime I am going to check if I have an extension, if not I create one. From then on I will reuse this one until my extension is shut down.

private WorkflowRuntime myWFRuntime
{
 get
 {
     myExtension ext ;
     if (OperationContext.Current.Host.Extensions.Find<myExtension>()==null)
     {
         ext = new myExtension();
         OperationContext.Current.Host.Extensions.Add<myExtension>(ext);
         return ext.WorkFlowRuntime;
     }
     else
        return OperationContext.Current.Host.Extensions.Find<myExtension>().WorkFlowRuntime;
 }

}

 

Is this a correct approach ?

Answer 4

That might be problematic due to race conditions — I don't think that ServiceHostBase.Extensions collecition is tread-safe. Attaching the workflow runtime during service activation is IMHO a better design.