Sharepoint 2010 Workflow: Create multiple tasks and change them

Question

I want to write a workflow which creates and updates tasks when the workflow item is changed. For example: the workflow-item has a multivalue field with users who should approve the workflow-item:

1. When the item is created, the workflow has to create a task for each approver
2. When the workflow-item is changed the workflow has to change the description of every task.

Part 1 (creation of multiple tasks) is more or less easy: I used a replicator activity (an example for this can be found in http://www.shillier.com/archive/2010/08/04/Creating_Multiple_and_Parallel_Tasks%20_in_SharePoint_2010_Workflow.aspx)

Part 2 (updating all tasks which were created in Part 1) is difficult:

I tried to write a CodeActivity, which iterates through all tasks and changes them via AlterTask-calls. This works perfect for the first time, but if I try to alter the same task a second time I get an exception, because the workflow has locked the task.

Another idea was to change the tasks with an UpdateTaskActivity. But this is difficult, because I have an arbitrary number of tasks and cannot define the right CorrelationToken for the UpdateTaskActivity.

Does anyone know a solution for this?

Answer 1

To prevent the error "This task is currently locked by a running workflow." try setting the WorkflowVersion of the task item to 1.

Example:

private void ResestTask(SPListItem task)
{
    // Remove the error "This task is currently locked by a running workflow."
    task[SPBuiltInFieldId.WorkflowVersion] = 1;

    // Update the task fields for example:
    task["Status"] = "In Progress";
    task.Update();
}