Mexican Rat Dog

I’ve recently had a need to model a looping workflow with a SharePoint Designer workflow.  Designer doesn’t have a ‘Start Workflow’ action available by default, so I installed the Useful SharePoint Designer Workflow Activities on Codeplex.

My workflow would be designed like this

1. Collect Data From Users with Task Form
2. Set Workflow Variable to Step 1 Task ID
3. Check for repeat condition on Above Task
   1. Start a new instance of this workflow
4. (Workflow Done)

Looks great, but when running this workflow, I kept getting the following error:

Exception from HRESULT: 0x8102009B

at Microsoft.SharePoint.Library.SPRequest.AddWorkflowToListItem(String bstrUrl, String bstrListName, Int32 lItemID, Int32 lItemLevel, Int32 lItemVersion, Guid workflowPackageId, Guid& pWorkflowInstanceId, Guid workflowTaskListId, String bstrStatusFieldInternalName, Int32 lAuthorId)

I searched around and found out that you cannot start an instance of a workflow on an item when the same workflow is already running on that item.  Lucy’s blog had a code sample which checked the target item for the duplicate WF and removed the WF if it was found.  I wanted to keep the data from the first workflow, and this would remove it.  Not exactly what I wanted.

Here’s a simpler approach I took:

Modify the original workflow (Workflow A)…

1. Collect Data From Users with Task Form
2. Set Workflow Variable to Step 1 Task ID
   1. Check for repeat condition on Above Task
   2. Start a new instance of the LookBack workflow
   3. Stop this workflow and log the message ‘Completed – Looping’
3. (Workflow Done)

Create a second workflow called ‘LoopBack’:

1. Pause for 1 minute
2. Start a new instance of Workflow A
3. (Workflow Done)

I can start an instance of LoopBack at the same time as Workflow A.  Then, LoopBack waits while Workflow A completes.  After that, it starts Workflow A over again.  The pause is there since Workflow A takes some time to fully complete.

Note, if you’re not running SP1, the Pause for 1 minute step will take 30 minutes to complete.  Installing SP1 will fix this issue.

This is a really simple way to model a looping workflow without going into Visual Studio.