WF4 - Resuming workflows with delay

Question

I'm trying to automatically resume workflows when the delay is over (using a delay activity) This is done automatically if you use WorkflowServiceHost, but I'm using WorkflowApplication.

There are a few codes on the internet that handle this, here is a sample I'm using WorkflowApplication to achieve these goals:

• A user create a task, and this task follow a workflow
• User design it's own workflow using a rehosted designer, and his workflow definition is saved in the database.
• Each workflow definitions can have different versions saved in the database to allow the user to modify its workflows, and the code use the correct version when an action is done on a task and it needs to resume bookmarks
• A task can be started using a workflow, so in the task table I store which workflow definition and which version is used for this task.

The problem I've now is when using delay activity Using the code linked above, when a runnable instance is detected I need to create a WorkflowApplication and use the LoadRunnableInstance method to load the workflow:

if (hasRunnableWorkflows)
{

    Console.WriteLine("Found runnable workflows");
    WorkflowApplication app = new WorkflowApplication(...);
    app.InstanceStore = store;
    app.LoadRunnableInstance();
}

Problem is:

• To call LoadRunnableInstance, I need to create the WorkflowApplication and so I need to give the root activity to the WorkflowApplication CTor
• To create the the root activity, I need to know which workflow (& version) I need to load from database
• To know which workflow to load, I need the task ID
• To know the task ID, I need to know the Workflow ID, which is only available after the call to LoadRunnableInstance

So ... I need to break this loop :)

Does someone know a way to have the Workflow ID before loading the workflow ?

Answer 1

The ControllingWorkflowApplications sample from the Microsoft wcf and wf samples shows that the system has to maintain it's list of workflow id's to know what workflows to load from the instance store. In that example, they also keep the path the workflow xaml file which should be able to handle your versions. That example isn't the easiest to follow but an extension to the WorkflowAppication that inherits from PeristenceIOParticipant is added to WorkflowApplication. This class extracts and defines the additional data that will be saved with the workflow. For your purposes that would be the id.

instance.Extensions.Add(() => new WorkflowDefinitionExtension(originalPath, connectionString)); //inherits from PeristenceIOParticipant

Answer 2

This worked for me.

When the Delay activity is hit by the workflow runtime, event PersistableIdle is fired and if it returns PersistableIdleAction.Persist then the Delay activity will be automatically resumed. If event handler returns PersistableIdleAction.Unload then the Delay activity won't be resumed automatically. Here is the Sample,

Workflow Definition:

Variable<string> name = new Variable<string>
{
    Name = "name"
};

wf = new Sequence
{
    Variables =
    {
      name
    },
    Activities =
    {
         new WriteLine()
         {
             Text = "Workflow Triggered"
         },    
         new Delay()
         {
             Duration = TimeSpan.FromSeconds(10)
         },
         new WriteLine()
         {
             Text = "Activity1 Completed"
         },
     }
 };

WorkflowApplication:

   WorkflowApplication wfApp = new WorkflowApplication(wf);
   wfApp.PersistableIdle = delegate (WorkflowApplicationIdleEventArgs e)
   {
         return PersistableIdleAction.Persist;
   };
   // Start the workflow.
   wfApp.Run();