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Pausing and Resuming a Workflow

.NET Framework 4

.NET Framework 4.5

This topic applies to Windows Workflow Foundation 4 (WF4).

Workflows will pause and resume in response to bookmarks and blocking activities such as Delay, but a workflow can also be explicitly paused, unloaded, and resumed by using persistence.

Pausing a Workflow

To pause a workflow, use Unload. This method requests that the workflow persist and unload, and will throw a TimeoutException if the workflow does not unload in 30 seconds.

try
{
    // attempt to unload will fail if the workflow is idle within a NoPersistZone
    application.Unload(TimeSpan.FromSeconds(5));
}
catch (TimeoutException e)
{
    Console.WriteLine(e.Message);
}

Resuming a Workflow

To resume a previously paused and unloaded workflow, use Load. This method loads a workflow from a persistence store into memory.

WorkflowApplication application = new WorkflowApplication(activity);
application.InstanceStore = instanceStore;
application.Load(id);

Example

The following code sample demonstrates how to pause and resume a workflow by using persistence.

static string bkName = "bkName";
static void Main(string[] args) 
{
    StartAndUnloadInstance();
}
        
static void StartAndUnloadInstance() 
{
    AutoResetEvent waitHandler = new AutoResetEvent(false);
    WorkflowApplication wfApp = new WorkflowApplication(GetDelayedWF());
    SqlWorkflowInstanceStore instanceStore = SetupSqlpersistenceStore();
    wfApp.InstanceStore = instanceStore;
    wfApp.Extensions.Add(SetupMyFileTrackingParticipant);
    wfApp.PersistableIdle = (e) => {          ///persists application state and remove it from memory 
    return PersistableIdleAction.Unload;
    };
    wfApp.Unloaded = (e) => {
        waitHandler.Set();
    };
    Guid id = wfApp.Id;
    wfApp.Run();
    waitHandler.WaitOne();
    LoadAndCompleteInstance(id);
}

static void LoadAndCompleteInstance(Guid id) 
{          
    Console.WriteLine("Press <enter> to load the persisted workflow");
    Console.ReadLine();
    AutoResetEvent waitHandler = new AutoResetEvent(false);
    WorkflowApplication wfApp = new WorkflowApplication(new Workflow1());
    wfApp.InstanceStore =
        new SqlWorkflowInstanceStore(ConfigurationManager.AppSettings["SqlWF4PersistenceConnectionString"].ToString());
    wfApp.Completed = (workflowApplicationCompletedEventArgs) => {
        Console.WriteLine("\nWorkflowApplication has Completed in the {0} state.",
            workflowApplicationCompletedEventArgs.CompletionState);
    };
    wfApp.Unloaded = (workflowApplicationEventArgs) => {
        Console.WriteLine("WorkflowApplication has Unloaded\n");
        waitHandler.Set();
    };
    wfApp.Load(id);
    wfApp.Run();
    waitHandler.WaitOne();
}
        
        
public static Activity GetDelayedWF() 
{
    return new Sequence {
        Activities ={
            new WriteLine{Text="Workflow Started"},
            new Delay{Duration=TimeSpan.FromSeconds(10)},
            new WriteLine{Text="Workflow Ended"}
        }
    };
}

private static SqlWorkflowInstanceStore SetupSqlpersistenceStore() 
{ 
     string connectionString = ConfigurationManager.AppSettings["SqlWF4PersistenceConnectionString"].ToString();
    SqlWorkflowInstanceStore sqlWFInstanceStore = new SqlWorkflowInstanceStore(connectionString);
    sqlWFInstanceStore.InstanceCompletionAction = InstanceCompletionAction.DeleteAll;
    InstanceHandle handle = sqlWFInstanceStore.CreateInstanceHandle();
    InstanceView view = sqlWFInstanceStore.Execute(handle, new CreateWorkflowOwnerCommand(), TimeSpan.FromSeconds(5));
    handle.Free();
    sqlWFInstanceStore.DefaultInstanceOwner = view.InstanceOwner;
    return sqlWFInstanceStore;
}

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