I've spend days trying to find a solution the problem i'm going to try to describe, i've googled alot and even looked at the .NET 4 reference source for SendReply and InternalSendReply activity. But until now i'm stuck.
To make the life of our end customers simpler i want to replace the Receive and SendReply activities with custom activites and use bookmarks instead.
I'm implementing a central webservice which can route to a correct workflow instance, that workflow modifies the bookmark value and finaly it creates a new bookmark while returning the modified bookmark value. It's rather complex already with a WorkflowServiceHostFactory which adds Behaviours and Attach a DataContractResolver to the endpoint.
The endpoint is derived from WorkflowHostingEndpoint which resolves a bookmark created in a custom activity (instead of a receive). And i want another activity instead of a sendreply. Those 2 should correlate and the custom sendreply does send a response on the open channel through the endpoint while creating a new bookmark.
The problem is that i didn't find a way yet to access the endpoint responseContext from within my custom send activity. On the other side, at the workflowcreating endpoint side, it seems that i'm not able to be notified whenever the workflow becomes Idle and as well i don't seem to be able to access the WorkflowExtensions from the host. i'm missing something?
A possible solution i've in mind might be not using a WorkflowServiceHost, but then i loose alot of AppFabric functionaly.
The workflowapplication in platform update 1 has some extension methods called RunEpisode with an overload Func called idleEventCallback. There it's possible to hook into the OnIdle and get a workflowextension to get the object to send back as response.
To answer my own question, i ended up in a workaround using the servicebroker functionality of sql server. The SqlDependency class where the workflow listens for the event to be fired whenever the workflow reach the activity that creates a new bookmark in another state.