Correct way to fix “This task is currently locked by a running workflow and cannot be edited”

Question

I have a SharePoint 2010 workflow that creates a task. The task has custom form and custom code executed when the form is submitted.

Inside the code I'm trying to set the Completed Status on the task when some conditions are met:

.....
SPListItem taskItem = this.workflowProperties.TaskList.GetItemById(...);
taskItem["Status"] = "Completed";
taskItem.Update();
......

I get this error:

This task is currently locked by a running workflow and cannot be edited

There are a lot of hits on this when you do a search and lots of fixes (workarounds?!).

My question is, what's the correct (or by the book) solution for fixing this?

Answer 1

This explains it in a clear way, along with the solution : http://blogs.code-counsel.net/Wouter/Lists/Posts/Post.aspx?ID=118

Answer 2

I eventually went for adding a UpdateTask activity in my workflow to update the properties I was interested in. It didn't involve any workaround code and I never got the "This task is currently locked by a running workflow and cannot be edited" since then.