How to programmatically start sharepoint workflow

SharePoint workflow is great way to automate the business process.  SharePoint workflow can be configured to start automatic or manually. But sometimes our requirement lies in between two default options i.e. we want to start workflow automatically if and only if certain condition met e.g.  workflow initiation depends on certain business logic or depends on some field value entered by user.  If condition met we need to start workflow otherwise not. In this scenario, SharePoint default options ( Automatic OR Manual) to start workflow do not work and developer requires to start workflow at run time using code.

To start a workflow at run-time  we need two important values: –

1. Workflow Association Reference Id OR Workflow association name: – Workflow association id that we want to start. OR workflow association name can also use to identify it.
2. Workflow Initiation Data: – Its optional but most of the workflow requires some initiation data. Initiation data that requires by workflow to take decision. To know more about the initiation data and how to pass it, please refer http://wp.me/p1nAw1-m

To start any workflow, we requires following objects: –

1. WorkflowManager: – With each SPSite object a SPWorkflowManager object is associated , enabling you to centrally control the workflow templates and instances across the site collection.  We can get WorkflowManager instace by SPSite instace.
   E.g.

    WorkflowManager = SPContext.Current.Web.Site.WorkflowManager;
   

2.  SPWorkflowAssociation: – Workflow association is a binding between list/library and workflow template.  When a workflow is added to SharePoint list/library an workflow association is crated. We can get the workflow association by list/library where workflow is associated.
3. E.g.

     SPWorkflowAssociationCollection associationColl = ParentList.WorkflowAssociations;
     foreach (SPWorkflowAssociation association in associationCollection) {
       // We can find the association by BaseId or by workflow association name.
       // if (String.Compare(objWorkflowAssociation.BaseId.ToString("B"), {"Workflow_GUID"}, true) == 0)
      // you can identify the workflow association by association name, entered during association creation.
     if (association.Name == wfName)        {
       association.AutoStartChange = true;
       association.AutoStartCreate = false;
       // We can change the
       association.AssociationData = string.Empty;
       // We can use other overload StartWorkflow methods.
      spSite.WorkflowManager.StartWorkflow(listItem, association,  association.AssociationData);
     }
   }
   

So complete code to start workflow at runtime is

public void StartWorkflow(SPListItem listItem, SPSite spSite, string wfName)  {
    SPList parentList = listItem.ParentList;
    SPWorkflowAssociationCollection associationCollection = parentList.WorkflowAssociations;
    foreach (SPWorkflowAssociation association in associationCollection)  {
      if (association.Name == wfName){
       association.AutoStartChange = true;
       association.AutoStartCreate = false;
       association.AssociationData = string.Empty;
       spSite.WorkflowManager.StartWorkflow(listItem, association,  association.AssociationData);
       }
     }
}